The “But it seems like new version has lots of problems” is a large over statement as there may be many who are experiencing problems, there are very more who have experienced no problems.
If this were a huge issue, then you really would see this forum light up.
Many of the issues (none that you mention or if you are experiencing any) have been resolved or partially resolved in the beta build that is currently running and the re-engineered files that some are testing outside of the beta program.
So things are moving along at what I would say is a reasonable pace, and the levels of posts have subsided.
Without dismissing the seriousness of the problems experienced by those experiencing problems :), I have and know of many XP PCs with avast! 4.8 and none are currently exhibiting bad behaviour. The 1178 beta seems to be as stable as an official release.
I think this is not due to avast problems but the users of the forums grow up a lot.
People is more active and more present at the forum.
I don’t think avast reputation has fallen down, on contrary.