I think most of the fault lies with Adobe for two reasons:
1. Extension Manager is a mess
2. Dreamweaver's handling of the cache file
You can get around most of this by remembering to remove an extension before installing a new version, and deleting the cache file after installing new extensions.
Solving problems with Dreamweaver
Updates are good because it mean bugs are being fixed.
Upgrades are good because we get more goodies. :)