Thanks for the posts, especially Manimac for breaking out the key distinctions--that's just what I was looking for.
I had an 800 MHz iMac back in January for about a week and returned it because of its apparent slowness and its <IMHO> relatively poor screen.
I've been using a 400 MHz Dell and I've been looking to switch for awhile now. I expected the iMac to be ~twice as fast, but to my surprise, although adequate, seemed slower in many instances. Also, although some are very happy with their iMac displays, I found it wreaked havoc with my eyes. After returning it to the Apple store, I discovered that the stand-alone displays were superior in all aspects from viewing angle to color, clarity, etc. (I assumed all Apple displays were equivalent ).
I, like many on this forum, find myself w a i t i n g for the next best release--looking for that magic bullet. I think a G5 iMac with a higher quality 19" display would've done it for me. But...
In terms of space/cost I'd prefer staying in the PB/iMac zone but my logic tells me that a G5 PM w/large display will keep me ahead of the Mac power curve and give my eyes a break.