Spiff,
That is one HELL of a deal.
Downsides:
socket 754: not supported for higher speed chips going forward by AMD but at this price who cares? You're not necessarily going to drop in a faster processor anyway...
AGP graphics: again, not future proofed, and you won't be able to shoe-horn the latest and greatest PCI-express video cards in there, but you could get a AGP class video card like the Nvidia 6600GT for $150 which would do you just fine for 3D gaming if that's your style.
Damn, that comes to around $300 for the core guts... not bad!! I may recommend this to some other folks...
~Josh