I'd say that a Mac makes a lot of sense as a general purpose computer. I have had a G5 iMac for about a month, and it's fantastic. The Mac way is a bit different at first, but you quickly get used to it. I've had a few niggles, mainly with wireless networking, but all-in it's easier to use and less work to keep running than my XP/Home desktop PC .
It's not quite up there in value for money when compared with a well-specced PC built by a specialist - although it's close, and beats out the typical high-street box-shifter PC. However, it wipes the floor with the PC for ease of use for the average user who just wants to surf the internet, write letters and use their digital camera etc. It falls down in a few areas though. Firstly, games. If games are your thing, don't buy a Mac. Full stop. Secondly, the higher-powered Macs are sexy machines, but don't IMHO offer good value for money. Unless you aren't bothered by price, buy a PC if you need loads of processing power. Finally, if you're reliant on any semi-specialist PC software then you're probably going to have to keep a PC around somewhere.
The latter reason is why I haven't been able to abandon the PC completely - there's assorted software that I can't do without or don't want to buy again. However, 90% of the time I'm using the Mac (he says, typing away on a PC running Firefox
).