Do you realize what you say makes no sense in some key aspects? No diss. intended, but here, I'll point out the flaws here in that post, this is just me though (some is fact, ofcourse) -
Ok, for starters, no PPC mac - or really any OS X box - was ever designed to be a gaming platform, and whilst there are games for them, they're not designed to have that be their forte, so really, if that's the incentive, then I'd say just get a console or a Windows box, really.
However, I agree for other aspects that the beefier chips in the PPC machines vs. the Mini by far are better and worth it, so yes, agreed there.
Finally, for making no sense: XP is still around and being "supported" (actually, I've yet to see any last updates for it) because businesses have yet to upgrade and people were still stuck in the "anti-Vista" state, and actually, correct me if I'm wrong, but, it's being no more supported than Leopard or even Tiger; the udpates are still on Apple's server to updated to 10.4.11 or 10.5.8, as with XP and SP3, but any more optimizations and bug fixes coming out for XP? I've yet to see any, but then again, for point 2 -
Vista w/ SP2 leaves XP in the dust. Fact.
MS had a bumpy (ok...disasterous) start with Vista, but with the SP updates some benchmarks even beat 7, though ofcourse all around 7 is king for Windows OS's.
On any relatively modern hardware (I'd say high end P4 rig and later), Vista SP2 or 7 will leave XP in the dust, on benchmarks and security so really -
That "downgrade" really was a DOWNGRADE as now your clients computer is less secure and less compatible, so gonna get it upgraded again?

Just a suggestion.
However, again, it would be a bummer for Safari to not be later supported on PPC, however, Apple should really pat themselves on the back for supporting a no-longer-supported architecture for them for six years, and counting..
And speaking of no support..IE9 - currently the best browser on Windows (great bowser TBH) - laughs at XP, and IE10 will laugh at Vista, which both (OS's) more or less came out around when PPC support was announced to be phased out.