Creating playlists: Have an option by pressing the menu bar, "add songs to playlist", which allows you to select which songs to add to a previously or "now playing" playlist, similarly to how you can "share" multiple photos at a time.
Quick search of songs/albums/artists by typing on the keyboard: This doesn't seem to work too well at the moment. I have roughly 2500 songs on my N900. I'd hope that typing would bring up pre-tagged music/video files by album, artist and song name.