BSOD issue in windows 8 was fixed in Avast 7.0.1474. ...that's what release notes say....there is some slowdown in startup except that no issue for me...
Changelog of latest version of Avast:
1. Win8 BSOD fixed (but still investigating some issues)
2. Crashes, freezes on WinXp 64b fixed
3. WebRep issues fixed
4. Sandbox stability improved