Has anything changed in the past 10 releases or so that would require me to upgrade my CPU from an Athlon XP 1800+?
Is that sarcasm? If not, apparently, you haven't heard the screams of a thousand mame users crying out in terror when Aaron rewrote the renderer/artwork system in MAME 107.
As usual, the CPU specs have been climbing. However with the renderer re-write, MAME now requires a somewhat modern video card now. Something at least DirectX 8.1 compliant, I imagine, and 64MB of onboard memory is probably a good idea if you plan on running any of the new ultra high res artwork that the new system requires.
There's some experimental multi-threading going on in the new renderer that can be turned on in 108 with an ini setting. It's just the renderer, not the game code that is multi-threaded so don't get your hopes up. It will only make a difference in certain borderline cases that are limited by the renderer.
Word on the street is that Intel Conroe (Core Duo) CPUs are the new speed champions for MAME. Plus, some of the low end models are VERY overclockable. At stock speeds, the Conroe chips are beating AMD chips, and overclocked, they're wiping the floor with their dead bodies.
Obviously, games that ran at 13 frames per second before are not going to be playable on anthing any time soon, including an overclocked Conroe. But the situation is certainly much improved.