Agreed. Spotify is my goto at work.
Some artists to counteract the gaps have released 'mixed' tracks (basically the CD as one long song so the spaces are gone where the track begins and ends) for Spotify, but gapless will be much better.
But, the more I use Spotify the more I see missing. Like, where is AC/DC? Zepplin? Damian Marley? THE BEATLES?! Some of the most prolific artists of certain genres aren't on there.
At first there was no 2pac on there. Which, since he's been added.
Is it licensing issues? On who's end?
Still an awesome service though, worth every penny.