I really love using Spotify and am very happy with the service.
This is literally the only thing that bugs me is when I find accuracy errors. For example the Lynard Skynard Greatest Hits (2005) album nearly every single song if not every song are named incorrectly (this is probably the record label's fault).
There are also times when I look for an artist and find there are two artists with the same name but their music has been grouped together under one artist e.g. search Knife Party and you'll find one album from some sort of rock band and then the rest is house/dubstep music all under one artist.
I've heard before all information is supplied by the record labels but maybe there is something you can do about these types of errors?
Other than this, congratulations on a superb service 🙂