I started AH using 6.1, then went to 7 when it was released, then 7a back in December. (I'm using a M$ Precision Pro (usb)) After the upgrade to 7 I noticed about a 2 to 5 fps increase

, but my stick spiked badly. That was solved with 7a (in fact it's even better than 6.1) and I kept the extra couple fps. I'd say if you have a fast connection, get 7a, it is better than 6.1. (Avoid Dx7, just get 7a.) I think it was a 7 MB download, but well worth it IMO.
bloom25
THUNDERBIRDS
Current system:
cel 400 on Al440Lx MB
Aureal Vortex 2 sound card, latest reference drivers
V770 ultra 4.02 drivers
96 mb ram