With most of these services you're bound to not be able to find a few songs. What's important is whether or not it fails gracefully into letting you manage those missing music files yourself and Spotify, Rhapsody, and Grooveshark are the only ones that let you do that to some extent.
True, but I expected them to have more deals in place. Most artists are missing key tracks, albums, or aren't represented at all. I also don't really think it's a few songs. Knowing my library and how mainstream it is, at least 8,000-10,000 tracks should have been matched. That's my library minus most independents and instrumentals.