I shan't be disabling avast, for some time, I will be blocking the IE7 download for a few reasons.
One, the download size is likely to be huge on a dial-up connection.
Two, I fully intend to wait for at least three months after going gold to see what comes up in the various newsletters relating to an issues.
Three, since IE is an integral part of your OS I'm in no hurry to find a problem that may compromise my OS.
Four, since IE (any version) isn't my primary or even secondary browser I will look after my own security without relying on IE7 during any initial period after gold release.