Not enough time to do a full report yet, so far everything looks good.
1. As you could tell from its file name, this beta only comes with English (mainly US English). so if you are using another language as well, make sure you get them from previous version before uninstalling them.
2. memory leak is minimal (2mb with 10 hours running time) with a lot of 3rd party app install. still a bit of too early to tell for sure.
3. browser is very fast compared to .52.
4. Wifi works fine and smooth. In my opinion, it doesn't lag as much as .52. B/c I don't use UMA, can't tell whether it works or not, someone else? =)