Dreamcast and emus...
The sega emulator is pretty good. Most games run at 95% - 100% of their real speed.
SNES is ok but the DC can only run these at around 60-80% of the real speed.
Playstation is another story. The hacked version of Bleem I tried was very impressive and runs Gran turismo flawlessly. It also runs a few other games at 100% as well. It struggles on Spyro but the game is still playable.
The NES emulator is great too and Mame is ok but you can only play the REALLY old classics (space invaders etc...)
Dreamcasts are pretty quiet - the drive makes a bit of noise when loading but thats it.
btw.. Because Ive now got my xbox the Dreamcast has got to go as no room so I will put the details in the 'for sale' section.
Ive also got a few Dreamcast to scart/phono leads left too (I won a batch of them on ebay and only needed one.) They are £5 each plus £1 p&p if anyones interested.