For Mac emulation, I use Basilisk JIT (version 0.8.1.142 I think, with OS8.1 and a Quadra 650 1meg ROM image and have had few problems with either utilities or games.
I run this on a PII-350/256meg/16meg Banshee, by the way. Beyond some very old titles that just don't seem to work, the only (admittedly minor) problem is that of an occasional glitch in sound playback (a very brief pause).
For reference, titles that I have comfortably used include 'Chuck Yeager's Advanced...', 'Doom' and 'MS Flight Sim 2'.
btw, I second Macintosh Garden, it's a great site and should keep you busy for a while