I think lessons with an instructor benefit everyone. I think it helps to keep you on track and keep you away from bad habits.

OK, so I'm a little biased as a teacher of music amongst other things, but I still take lessons myself. It also helps you stay away from 'traps' like Benoit explained that he played only metal. I always introduce other material around the student's preferred path.

I learnt classical guitar from the age of 8, then Jazz from 14 - I shred like crazy now, but I didn't play an electric guitar or any form of 'rock' until I was 15. Having the grounding in all sorts of techniques really heelped me fly, and now I can add different techniques in. For instance, I hybrid pick way more than the other guys I play with - they alternate pick almost all the time. Nothing wrong with that, but I can do the things they can do, and I've got a few tricks in the bag to surprise them with!

If money is OK, I strongly suggest you take the occaisional lesson to keep yourself on track. You can teach yourself, but I think you'll get further faster with a good teacher...