Dear Sindre,
thanks for developping the Subsonic project, it's great to use it. The Android app is now my main music player on my Samsung galasy S4 (version 4.4 from F-droid). Last days I had the occasion to use it a lot and I have some feedback for you, so you may consider improving it:
1) playing a song that is not yet cached works at first, but the song restarts after ~30 s of playing, even if caching is complete. It is apparently systematic (LAN wifi and 3G, various bitrates), and very annoying. I think this has been reported before by other users.
2) directory listing does not work for big folders (500+ songs typically). I had to split big folders in smaller pieces to view their content.
3) when you search for a song, you are redirected to the directory which contains it. this is ok for small folders, like albums with 10 files. It is not ok for 100+ files folders, where you have to manually scroll until you see the song. At least the result of the search should be highlighted.
4) in the library's lists, it is difficult to click on the vertical three point buttons on the right, because instead it activates the vertical scrollbar. I suggest that you move this button elsewhere in the user interface or that you dedicate space to the vertical scroll bar.
5) when you are in the library, click on "play now" on a song, you are redirected to the "player" tab. if you wish to play another song of the same album and go back to the library, you are back to the root folder of the repository. you have to go through all the folders to go back where I left the tab. I would rather go back where I were when I first clicked "play now". tl;dr : please don't reset the state of the "library" tab when you leave it.
6) (low priority) you might consider implementing the automatic playlists based on last.fm, as in the web client, if it is feasible. If they are present, I did not see them.
7) I noticed some annoying freezes during playback, which recovered after a few seconds. Difficult to say in what conditions (which seem random), so it will be difficult for you to debug this.
I am ready to discuss and to help debug point #1, which seems the most critical in my opinion.
Kind regards