How can i find the version nr?
I think the easiest way is to use the web manangement tool. If it is a nighltly build, it will say what daap version you have in the server status view or in the about firefly view.
The nighlty download page is at http://nightlies.mt-daapd.org/ so you can check if there is a newer version you want to manually update to. If you are using unslung, the package manager (ipkg update && ipkg upgrade) will not update nighlty builds unless you add the firefly nighlty feed to the ipkg sourcelist, but if your client devices can access firefly without complications, there really is no need to update all the time.
Some suggest that nighlties have better compatibility with clients other than iTunes such as the Roku SB with only svn-14xx and XBMC with svn-1498 or newer.