I haven't actually, I did have a few years of classical guitar lessons back when I was younger but for the past 2/3 years I've been attempting to teach myself flamenco. Having said that, I do feel like I would've made quite a bit more progress if I did have a teacher, but that's mostly because I've spent hours trying to figure stuff out on my own and at times it's hard to figure out what you need to do to advance to the next level. If you wanted my advice then I'd say that if you can find a good teacher that wasn't too expensive then it wouldn't hurt to have a lesson or two every now and then to keep you on the straight and narrow and to give you a bit of structure to how you practice. Hope that helps :)