I'm running a 16x16 Fort.
My dwarf population is at 55, 16 or so animals, and about 15 pages of wildlife.
Features: 65 z-levels.
Brook
Underground Pool
Underground River
Chasm
Bottomless Pit
Magma Pool
Magma Pipe
HFS
My FPS runs at 30~ (lower if I have a lot of verticle effecting mining designations). It doesn't seem to vary much even if my dwarves are doing a lot of pathing. Mind you, pathing is all they do, I'm making stone blocks and ash (for clear and crystal glass) out the ass.
I curently have my core 2 duo (2.66GHZ) overclocked to 2.95GHZ. Tommorow I'll probably up it a bit, as the fan seems to be doing a good job of keeping it cool. (About 30 for the processor, 37 for ht board)
After I upgrade to 8GB of ram, I'll post 3D picks (I currently cap out at 48/65 with 4GB)
Other things to note: I'm running this fort on a Vista 64bit Ultimate
My embark groups name is thus: Steelfists the Crystalline Destroyer, at the site of Crystalline Fortress. And believe me, that name never gets old, no matter how many times you read it.
I'm attempting my own 300 year Armok Megafort Project. .... I'm currently on year 2.5
Edit: Working on individual megaprojects before your asured survival spells certain doom. Moreso when a human invader crossbowman with a max strength stat shoots your champions, and then proceeds to club your citizens to death.