Did they already up the total number of songs? Can't tell or not, but it seems to let me upload 35k.
I think that was just an advertised number then. I thought my dev rights allowed me to upload my 44K songs, but it looks like they haven't blocked anybody (yet). I've been adding songs from my initial upload and it's still not telling me I have too many songs.
A couple of things that have caused problems for me. (1) I didn't wipe my phone's SD card clean before I used Google Music, so now I have doubles of some stuff on my phone and there's no way of telling which is the local version and which is the online version. That will be problematic on say a plane or in a tunnel on public transportation. I recommend clearing your phone of your music first, then installing Google Music, and then transfer songs back to your phone, if you so desire, afterwards. (2) I'm not exactly clear which version of IP tags Google Music is using, but it doesn't seem to be consistent (or maybe it's my collection, but I've spent years trying to rectify this), however, the ability to edit from the cloud as made this a non-factor. Amazon should take note.