Build 50 (beta 20 for kernel 2.6-based builds) is available for download.
Although there are still some known issues I need to research further and resolve (see, for example, forum threads regarding DIR-320 router, MiniDLNA, and a few others), I still wanted to get a new build out as soon as possible.
First of all, it contains a few very important changes: fix for Media Server deleting all your media files, fix for DNS rebinding protection disabling some legitimate services and change to make this protection optional. Also, there are some new features I would like to get a feedback and bug reports about (Web Monitor, dual-band support) - it's always better to address bugs earlier, before the cause gets obscured behind lots of new changes…
Please read the Changelog to find out more.