I just replaced my crossfire 6950's with 7950's,No issues whatsoever,had the 6950's for 2 years with 0 issues.
The 7950's for about a month.
Crossfire works like a charm,almost 100% scaling in BF3 and BF4 on all drivers to date.I do nothing out of the ordinary,I dont even uninstall the old drivers,just install the new ones over the old.
And i have never,nor will ever use a driver/registry cleaner.
AMD Phenom II 1100t @4.0Ghz /Asus sabertooth 990fx/2x Gigabyte 3G 7950's in crossfire/500G samsung 840 ssd/16G G-Skill Ripjaw 1600/2-samsung 24" monitors 1920X1200/Corsair AX1200W psu/W7 pro 64,G19 keyboard,Roccat kone pure mouse,Cooler master HAF932,Corsair H100i water cooler,Zalman ram cooler.Sound Blaster X-Fi Titanium Fatal1ty Champion Series,Logitech Z5500 speakers,Roccat Kave 5.1 headset.