Intel core 2 duo. This is my third upgrade in as many years, I actually feel quite ashamed (almost) to say that because I sound like a spoilt brat but I work hard and pay for own stuff, which I guess makes me entitled to spend it on what I enjoy.
Only two real upgrades anyway, my first Mac (emac) was just really a taster machine as I'd never used a Mac before; justification ahoy.
2 GHz 17" iMac G5. Before that I had a Motorola StarMax 4000 Power Mac clone which had a 160 MHz PPC 604e CPU. I hope to get either a MacBook or MacBook Pro sometime late next year.
My newest machine is G4-based (see sig). Probably won't upgrade until Leopard's release at the earliest. Typically I upgrade every 4 years, but with the Intel switch I think I'll want to move more quickly.
You know, I just realized that the 68K Macs were left out. While probably not used as much as the PPC or Intel Macs, I know I still use my Quadra 650 (MC68040 CPU) for sequencing music as well as some MP3 streaming with MpegDec. It's also an HTTP and FTP server. My PowerBook Duo 230 (MC68030 CPU) is sitting quietly in a shelf for now.
I switched from a PC to a Mac in the Spring. I bought my iBook one month before they switched to the Intel ... so, last week, after the MacBook upgrade, I bought the 2Ghz model ... and LOVE IT!
i think my favourite thing about lcd's is that they allow the desk to be reclaimed as being a desk. i can have A3 sketchbooks between me, my keyboard and my screen now. that's wonderful.