I can confirm that Avast 7 severely slows down windows 7 64-bit. I clean installed windows 7 64-bit on my fiancee's Alienware m14x and installed Avast 7 Free after all windows updates were installed, along with Comodo Firewall Free. I noticed start-up took almost 2 minutes to fully load. Before this fresh install, with Avast 6 on the same notebook prior, start-up would take approximately 30 seconds.
So I downloaded Soluto, AFTER JUST EYEBALLING THE 2 MINUTE START-UP WITH AVAST 7 AFTER A FEW MORE RESTARTS, and confirmed Avast 7 was the culprit taking 88 seconds to load. So I disabled Comodo Firewall thinking this might be affect Avast 7 and restarted 3 times, and Soluto still showed about 80 seconds for Avast 7 to load. Consequently, I uninstalled Comodo Firewall thinking this might solve the problem and restarted the laptop 3 more times and can verify Avast took roughly 80 seconds each time for windows to fully start-up.
I also tried the Avast 7 beta 3, to no avail. The long start-up time still exists.
It's clear that there is a problem with Avast 7, and seems ifAvast has dropped the ball on there latest version and Windows 7 64-bit.