I love telling Windows fan-boys about how many years of excellent service my Mac has given me. Then I tell them that Macs cost less than Pee Cees because they cost less per year of service.
Excellent. I'm in the same boat, posting this from a Sawtooth 500 --> Dual 1.2Ghz, 1.5GB RAM. Kind of mind blowing to think our motherboards are downright paleolithic by computing standards and still chugging along like little champs. I myself opted out of 10.5 until I finally feel the final itch to get new iron. Guess that'll be once enough software stops supporting Tiger (and PowerPC). Flash video is the only real bummer on this 100mhz FSB (ugh not even 133mhz). I think the power supply's finally giving up. Whenever the CPUs get thread heavy you can actually hear the fans slow down a couple notches at this point.
Previous to this I owned a 1st Gen 601 60mhz upgraded to 266 (via PDS/NuBus slot) which itself lasted me 6 years of loyal service.
The sooner you fall behind, the more time you have to catch up.