Alpha testing for 0.5.0 is coming to an end. I'm releasing a full 0.5.0 version based on a 6 week old alpha. So all the new features and fixes from over the last 6 weeks are not in there. If you are playing alpha's newer than that, don't bother updating to the full version.
The reason for such an 'old' version to become the release is simple: Lots of exciting things are possible without the dll, but with that loads of new possibilities for bugs to be introduced. The version that has become 0.5.0 should be stable enough and be a big upgrade for the people only playing full versions, and alpha's will soon be released for 0.5.1, the first one will contain all the changes from between build 3080 (release) and the first alpha for the next release version.
If you have an alpha version from 3073 or newer, you could simply overwrite it with new alpha's released for 0.5.1, no need for a fresh install.