I just went from a 5870 1Gb to a Sapphire 7950 OC 950mhz (Oc'd to 1150/1400) and if you like turning stuff up, it's a good buy.
I'm at 1080p/60hz and with the 5870, I had BF3 framerate limited to 59fps (performed way better than not doing it) with all ultra/no MSAA/high FXAA and stayed mostly in the high 50's with the odd drop to mid/late 40's.
With the new card OC'd, I can play at full ultra (4xMSAA) with it sticking at 59fps occasionally dropping to 47fps at worst. I usually leave it on 2xMSAA and only drop to 55fps at worst, and only on rare occasions.
Don't know about max fps as I wouldn't be able to see it on my screen anyway.
Oh, at this OC it scores 1957 on Heaven fwiw. (Tessalation - Normal / 4xAA)
Hope that helps
EDIT: Forgot to mention this is with 12.9 beta / 12.9 Cap1. Min fps improved a bit with these over 12.8 (which I didn't have any issues with)
EDIT 2: If you're doing ok with your current card, it may well prove worth waiting for the 8xxxx series unless your upgrade itch must be scratched NAOW! Mine did Edited by Speshy - 9/27/12 at 11:08am