I have songsterr, but the tabs are somewhat low quality for all but the most popular songs. I just bought "The Best of Opeth" and "The Best of Foo Fighters" book tabs, and they are sooo much more detailed and better than any app I've found, which is great. Not that I'm skilled enough to make it through any Opeth song... but playing their spooky chords is fun.
I also have a "25 Top Post-Grunge Rock Songs" tab book which is neat.
P.S. I'll send pictures of individual song tabs from these books if anyone is interested.