Hey, John! I also believe in using good hardware as long as possible.
I'm using a Gigabit DP machine that's been upped to dual 1.2GHZ G4s and am switching it to a SATA RAID controller to squeak another year or two out of it, although I'm really starting to see a need for an Intel Mac ... or a Hackintosh (which I would dual boot in Linux (and maybe one or two other O/Ses I want to play with.) I have an old MACmini Intel that I can use, but the thing is so underpowered and unpleasant to work on that the thought makes me cringe every time.
The PowerMacs in the Blue & White through MDD series were just beautiful boxes that are a pleasure to keep upgrading.
I also used my WallStreet for many years, and with the SCSI and the Ethernet on the back I had all I needed, and I'd get a kick out of plugging it into the back of big SPARC servers and configure and set them up - showing up with this cute little laptop and firing up a rack full of equipment with it used to give me such a laugh. I need to resurrect it to be a print server and music streamer on my home network....
My project after that is to set up some software on my old iMac G3, plug in one of those abuse resistant "kiddie" keyboards, and let my 3 year old have his own computer. Would give my wife and I some relief if he can watch Bob the Builder on his own machine, and start "typing" and using his own mouse, instead of ours.

Many of these Apple models just keep going for years and years and years. How many people would still get use out of a Wintel box they bought in 1998 or 2001?