I taught myself for a year when I started, and I did fine. In fact, when I got a teacher the following year, she said I was a couple years ahead of where most people would be having played as long as I had. So that was pretty cool.

The only thing I remember really improving on through lessons was fingering. When I was teaching myself, I would tend to always play certain chords with certain fingers on certain strings. Then when I started doing jazz and classical stuff in my later lessons, she taught me the fine art of choosing the most efficient finger for the note. It helped a LOT.

I would say take the lessons. You may be doing fine, but it never hurts to have someone examine your playing style and give you tips on stuff you might be totally overlooking.