@Pennington - Very good point with the Cave problem, but wouldn't it be more or less dropped if the people in Heaven remember pain and heartbreak from their life on earth, and the people in Hell remember how great a cooling swim was on a hot day? (stupid examples, but still)
As for speculation on what to expect, (which as asaris says it's ALL speculation), My personal hope goes something like this :
Think of some of the top things you like to do. I'm mean really, truly enjoy doing, I don't mean just fucking someone cause 'it's like um sex and uh it feels good'. I mean like the feeling you when you grab the woman you love or nail that drop on your mt bike you've been scared shitless of for the past year or finally cresting that ridge after a couple of days hiking and look into the pristine valley below you. Oh yeah, and the ability to explore the universe, all of it. I'm going to be pissed off if I can't bomb around at super light speeds and check out all of creation. Infinite time + infinite space = lots of things to look at!
Hell on the other hand? My personal view was actually pretty similar to what showed up in that godawful movie Event Horizon. Chaos, pain, horror, endless.
Of course, I could be utterly wrong. The best part is there is only one way to truly find out. So it's damned fun to talk about.
@Macheath - Nah, I always figured most of the classical philosophers would be hanging out getting drunk and laughing about how wrong/right they were... And if they're having fun, well, that kinda rules out the hell part of it. (Dante's thoughts notwithstanding)