IMHO, the answer to the initial question (would it be worth it to kill ourselves if there was Nibbana—as cessation—after death?) is no. Nibbana, if it’s the mere cessation of the aggregates, doesn’t seem very appealing without rebirth. This beginless stream of existence is tiring, stressful, and unsatisfactory, but, without rebirth, existence isn’t that bad. We actually would have just one life and inevitably reach Nibbana at the end, so there wouldn’t be much point in killing ourselves.
This thread has given rise to a lot of bad reactions, so I’ll move to discuss the fear of Parinibbana. My observation is that this reaction has nothing to do with the discussion of the nature of Nibbana. Whether or not it is a supramundane state attained by arahats, it should cause fear to anyone who is neither a suicidal nor a stream-enterer. That is, if you have identity-view (i.e. you see yourself as, in, possessing, or containing one or more aggregates), then Parinibbana will mean annihilation to you. If you actually didn’t fear it and still had identity-view, then it would either be because you didn’t mind being annihilated or because you misinterpreted it as a state wherein some aggregate remains. Whether or not Parinibbana is a state or not is beside the point: what matters is that all of this that you identify with, that you hold dear, that you take care of, will be utterly destroyed.
Of course, this sounds horrible. The worst is that the view of Parinibbana as a state doesn’t solve the problem at all. In fact, if it were some state, what would be the point if there will be no consciousness in it? (supposing that you identify yourself with your consciousness). In other words, that state wouldn’t be attained by “you” anyways since what you identify yourself with will be absent.
I believe the solution lies in recognizing that the happiness in Parinibbana is of a sublime sort, and it can’t be comprehended easily. Most people can’t even see how a life of renunciation may lead to happiness, let alone something devoid of the five aggregates. That’s why the Buddha wouldn’t go around teaching every lay person about Parinibbana. Rather, he would instigate people to pursue higher forms of happiness or teach them how to attain morally what they recognized as happiness. Practicing compassion, generosity, virtue, Kamma, and rebirth leads to a better life here and now, but even that is not enough, so the person may move on to renounce indulgence in sensual pleasures and start practicing meditation. After each attainment, the person sees the drawbacks of that and pursues more refined sorts of happiness. Only when they’re mature enough, awakening will seem appealing.
Admiring such a goal is difficult because we don’t know how the lack of feeling could be good. Fortunately, the following excerpt may provide elucidation:
“Now, it’s possible, Ānanda, that some wanderers of other persuasions might say, ‘Gotama the contemplative speaks of the cessation of perception & feeling and yet describes it as pleasure. What is this? How is this?’ When they say that, they are to be told, ‘It’s not the case, friends, that the Blessed One describes only pleasant feeling as included under pleasure. Wherever pleasure is found, in whatever terms, the Blessed One describes it as pleasure.’”
MN 59
This means that something may be pleasurable even though it doesn’t have any feeling. We can’t recognize this truth only because of our ignorance.
If we find Parinibbana fearful, then we should focus on the mundane part of the path, like virtue, generosity, and compassion. In the meanwhile, we may interpret our fear as coming from false misconceptions that the Buddha himself had correctly overcome, and it’s out of faith in his good intentions for teaching that we may believe that Parinibbana is truly worth it, even though we may not recognize that now.
After addressing the main question and the fear of Parinibbana, I’m going to share my views on the nature of this state:
- In the Kotthita Sutta (AN 4.174), Ven. Sariputta explains that one can’t claim that there is, is not, both is and is not, and neither is nor is not anything in Parinibbana. Therefore, the view that it is just the cessation of all khandas with nothing else is as wrong as the view that there will be something in it;
- Nibbana is a thing. If it were just the lack of anything at all, it would be nothingness. So the state of perception of nothingness could be said of being the perception of Parinibbana. However, the meditative attainment wherein one is percipient of Parinibbana is described in the Sāriputta Sutta (AN 10:7) as being attained only after one has surpassed the perception of nothingness:
“Once, friend Ānanda, when I was staying right here near Sāvatthī in the Grove of the Blind, I reached concentration in such a way that I was neither percipient of earth with regard to earth… nor of water with regard to water, nor of fire… wind… the dimension of the infinitude of space… the dimension of the infinitude of consciousness… the dimension of nothingness… the dimension of neither perception nor non-perception… this world… nor of the next world with regard to the next world, and yet I was still percipient.”
“But what, friend Sāriputta, were you percipient of at that time?”
“‘The cessation of becoming—unbinding—the cessation of becoming—unbinding’: One perception arose in me, friend Ānanda, as another perception ceased. Just as in a blazing woodchip fire, one flame arises as another flame ceases, even so, ‘The cessation of becoming—unbinding—the cessation of becoming—unbinding’: One perception arose in me as another one ceased. I was percipient at that time of ‘The cessation of becoming—unbinding.’”
- From the logical standpoint, if Parinibbana were nothing, it couldn’t be said to possess properties. We wouldn’t be able to call it “unborn,” “unfabricated,” and “deathless.” Instead, we would be right in claiming, “there is no unborn, unfabricated, or deathless.” In other words, if there were nothing that matched these properties, it would make no sense in describing it. However, the Buddha said:
"Now these three are unfabricated characteristics of what is unfabricated. Which three? No arising is discernible, no passing away is discernible, no alteration while staying is discernible.”
AN 3:47
“There is that dimension, monks, where there is neither earth, nor water, nor fire, nor wind; neither dimension of the infinitude of space, nor dimension of the infinitude of consciousness, nor dimension of nothingness, nor dimension of neither perception nor non-perception; neither this world, nor the next world, nor sun, nor moon. And there, I say, there is neither coming, nor going, nor staying; neither passing away nor arising: unestablished, unevolving, without support [mental object]. This, just this, is the end of stress.”
Ud 8.1
- Even though it is not nothing, it’s still not some eternal paradise. The solution to this dichotomy seems to lie precisely in its ineffability:
The Blessed One said, “What is the All? Simply the eye & forms, ear & sounds, nose & aromas, tongue & flavors, body & tactile sensations, intellect & ideas. This, monks, is called the All. Anyone who would say, ‘Repudiating this All, I will describe another,’ if questioned on what exactly might be the grounds for his statement, would be unable to explain and, furthermore, would be put to grief. Why? Because it lies beyond range.”
SN 35:23
Given that Nibbana will consist in the cessation of the All, it’s not possible to describe it. When we try to do that, we end up depicting it as if it were made of aggregates: we imagine a black, void, and neutral existence, a state of consciousness full of bliss, or maybe just nothingness. No matter how hard we try, we will end up misrepresenting it.
While we still don’t have direct knowledge of Parinibbana, we should focus on what the Buddha told us: it is the highest happiness (Dhp 203).
. That is already enough of a reason to take up the practice. Ones immediate life, and that of those in ones orbit is improved, the practice of Sila is being a friend to oneself and others, and easy to see in the here and now 
there appears to be a conflation of nibbāna with residue and nibbāna without residue (parinibbāna), in your response.