It's acceptable for what I need to do. Screen redraw time is quite a bit slower, I notice that on one of my programs that displays realtime waveform data from a seismic recorder. I wouldn't try to do any multimedia type stuff on it. I ran a few tests using Delphi 5 and a couple of the programs I've written with it on both a 1.2Ghz athlon (PC) and the 1.4Ghz G4 using Virtual PC (VPC):
Build large program: 1-2seconds (PC), 5 seconds (VPC)
Start large program: <1 second (PC), 4 seconds (VPC)
Download compressed seismic data from fairly slow data logger (which I think is where much of the time is coming from), decompress, and graph: 19 seconds (PC), 21 seconds (VPC)
Same data as above, by apply IIR filter: 6 seconds (PC), 9 seconds (VPC)
So it all depends on what you are doing. If the program is waiting for you, or for another computer for a significant amount of time, then the speed difference isn't that great.
Note that there are a number of PC emulators. I also tried the cheaper "Guest PC" but it was really too slow to be useful for my purposes, especially screen redraw time.
Virtual PC (from Micro$oft) can be bought with either Win 2000 or XP, people recommend 2000 since XP is so much more bloated. If you have specific questions you might try this forum:
http://www.macforumz.com/modules.php?na ... Virtual-PC