I suppose in the end it all boils down to what you need and what you don't. For people who use their Macs for business, obviously it would be quite a poor decision to invest in any PPC technology at this point in time. But for your average computer user, I still stand by the idea that most of the later G4's and the G5's are all they need.
I myself use a 5 year old eMac with a G4 in it as my daily computer. Just a 1.42 GHz single core processor, and a measly 512 MB of RAM. But I don't need anything more then that. Just basic web surfing (No flash), IM'ing, iTunes use, a small amount of photo editing and the occasional game or two. And really, how many people actually do more then that on their new machines that they buy today? It just seems like a huge waste of money when you can get something four times cheaper that does everything you need. But hey, maybe that's just me.