I guess I got lucky when the first world I genned had exactly what I wanted as an embarkable area?
Or perhaps finder only considers the ones which are ok, which might be a useful workaround for those having difficulties.
I am only seeing 80fps with 21 dwarves, where typical was >100fps (starts at 200) and it took more like 50 to make a dent in fps on .12. But it could be map dependent, one sample is insufficient to make a judgment. It dropped upon breaching the underworld, so I thought maybe it was critters, but the unit list shows nothing down there. No running water, and don't have the dfhack yet to check for a magma waterfall.
On those asking the Win2K user why s/he doesn't upgrade, I'd guess not a powerful enough computer. You can't get XP any more, and Vista/7 have pretty high hardware requirements. And some Windows users are not ready for the challenge fun of linux. Most people who hate Vista were already Windows experts (or at least comfortable) to begin with, and some of the "features" are really annoying if you're used to being able to do anything you want to your own computer. Win7 is a little better, but there are still files and directories I can't look at. Not acceptable behavior in an OS. But if you want existing programs to be guaranteed to work...
It would not make sense to require 64 bit, since likely half of the user base or more are on 32 bit machines. Memory usage is always a case of getting it to work, and then optimizing it. I think you'll see a pattern that when a feature is added memory usage will spike, and then maybe it will go down with maturity. Also being frugal with memory might result in less efficient processing, which leads to lower FPS. Some things might be a byte where a bit will do or a word instead of a byte, but all that bit testing / shifting / and/or logic adds CPU.