I'm typing this on my PowerMac G5 1.6, bought from e-bay for less than $1000 even.
I loaded it up with 2gb of RAM. Runs great. And I 2nd what others say...I've owned mac's before, and I just got it cause I love doing creative work...say 3d rendering or animation on the Mac...it's just a fun computer that I like to do fun things with....at work I stay mostly in the Unix world...and I keep meaning to put oracle on this thing...but actually, despite its geek potential, I've stayed busy without geeking it up, just yet (that may change soon, though, fink, mono, xmlrpc, xmlblaster....ooh la la)
darn it I started slobbering and forgot what I was saying...
anyway, oh yes....I never realized how much time I had come to constantly waste on these stupid virus's on the pc....now I always surf on the mac, and my very high spec'd pc, just is used for the occasional tunnel into work.
as for a sub 600 mac....Apple needs it. I don't think it will be a world beater, as people play games, and pc's have the most games....but, for those who were really in the Mac camp, but just couldn't stomach the high price of the Mac (and it is really high)...they can finally purchase a new machine. And I can see how amigans, who are naturally curious about alternative os's..would certainly want one too.
I still think linux runs better,faster on x86, however.