I know, right? A few years back I was interested in the concept of PS2 emulation until I found out that games only ran (if at all) at 1-2 fps and a 2 minute demo recording took hours to make.
Fast forward 2 years and the emulator furthest down the line -PCSX2- is doing very well. So much so in fact that some games are running full speed with a respectable compatibility list to boot. Of course the nature of the beast is that your favourite game probably doesn't run properly yet, and for me that's Ace Combat 4 and 5. The exception being if your favourite game starts with Final and ends in a number..
There are some other downsides; you'll need a fairly beastie PC and at least windows Vista (Slowsta more like) or win7 for directX 10. XP and DX9 is supported but the emulator is is optimized as DX10. On an AMD 7750 dual core running at 2x 3ghz with an Ati 4850 I get around 75% of full speed in a demanding game like Gran Turismo, in some areas it briefly smooths out to 100% but drops in an open area. You can expect more fps for most games, Seek and Destroy for example runs at constant full speed.
As you can see from the screenshots, when a game does run without graphic glitches it looks gorgeous. Controller functionality is good and its fairly easy to setup a joystick; the prospect of using my Saitek X52 stick/throttle in Ace Combat is positively drool worthy. In a cruel twist of fate, the mediocre Rebel Raiders runs quite well and is almost enjoyable with a joystick.
You can get PCSX2 from here. Check the PCSX2 forums for the latest (unsupported) beta and plugin versions if you have problems with a game. Definately one to keep an eye on.