I'm always in two minds about guitar sample libraries. On the one hand, I'm a more than capable guitarist, have a beautiful sounding steel string, an American Telecaster and a couple of very good mics. On the other hand, I've never worked out how to deal with the fan noise and street noise my mics pick up, and my Telecaster has unbearable buzz with high gain sounds.
So I go to look at guitar libraries, and then I can't bring myself to lay the money down because it just seems like I should be doing more to fix my guitar recording problems instead.
One exception recently was with the strummed acoustic library you get with Komplete Ultimate. I hated it at first, but recently used it to add some simple muted strumming to a track and it sounds soooo good.