Like the OP I built a rig not too long ago specifically to have AGP. 3777's "intangible" comment does make a bit of sense if you're more of a hardware junkie than a gamer, which I am.
I mean heck, I could have built a cheaper AM2+ x2 rig with PCIE and DDR2, but I wanted to have AGP, DDR1 and Socket 939.
Both of my rigs run Vista (although my x3 720 rig runs x64) and the speed difference is just a little bit noticeable in the resolutions I run at.
It's really fun to fire up my "vintage" rig and play newer games at high settings.
Granted, my rig's not as fast as Carl ASROCK Weathers
but it still holds its own against non-OC'ed C2Ds and most x2 cpus, and its video performance from the PCB OF DOOMŪ
Radeon HD3850 is stellar to say the least.
I get the musclecar analogy. It's a bit of a stretch but it makes sense. Take a Pontiac Tempest, turn it into a GTO and race a new 'Stang and you get a similar sense of gratification..... but more so.