Here is one common counter-argument to the notion that death is simply a transition to a hitherto unknown form of existence:
"You're just changing form" — This argument has its roots in new agey concepts that borrow liberally and inaccurately from dead religions and a Dummy's Guide to Buddhism. In various forms it states that what constitutes the essential "me" will continue in the redistributed particles that formerly comprised my body. The problem: no mechanism for this association has ever been established. ... The precise thing I'm attached to is my train of thought and my ability to experience sensory input. There is no other "me" that I care about, because that's the only part of me that cares about anything.
This is a tough one to tussle with, because on a factual level, he's right, and in most of the discussion I've encountered with Western Zen Buddhists (and even a few non-Western ones), there is no question about the finality of death. Some people question the point of having such a worldview since it provides you with no real comfort anyway — you're dead, but at least the bits of you that were once you are still floating around through the rest of the universe for all time. Oh, thanks; that just puts me right at ease.
Like most any belief system or practice path with a label, Buddhism is more of a conceptual spectrum than a fixed entity. Some Buddhists believe in reincarnation, because it fits nicely with the theological framework that existed before Buddhism came along; some don't. I don't, because the evidence doesn't suggest that death is anything but final and complete as far as our consciousness is concerned.
Okay, so why take this "you will always exist in this universe in some form" point of view at all, except as a sop to the emotions? My feeling is that it's one of those things you can take if you want, or leave if you want; it's not mandatory. I don't particularly want to die, but I also know better than to think I'm going to have much of a chance at living more than the average lifespan of a human being in my default circumstances.
I kind of like the idea that "I" am going to continue in some form, even if it's one that doesn't have anything like sentience as we know it — but at the same time, I'm not about to turn that idea into an excuse. I won't try to sell others on it, and I won't use it to try and get out of anything — especially not the obligation to make the best possible use of my life while I have it as I know it. Besides, if you only get one shot at existing, you might as well make the most of it, right?