I would definitely take lessons from a better player.
It's tough though, because different players have different styles. Dan Harrington v. Daniel N., for instance.
Are you interested in adopting someone's style of play or just see what they have to offer and take what you want from it? The answer to this question, I guess depends on how good your teacher is, and whether or not you want to blindly accept everything he/she says.
Another question you have to ask yourself is: What are you doing this for? Are you interested in making this a career, or do you play as a hobby - hoping to make a few bucks? If you're interested in poker as a career, I would think a mentor is extremely necessary. Not even all poker knowledge, but things like money management, bluffing, choosing games, tournament play, and the list goes on. On the other hand, if you are just having a good time and would like to make a few bucks, I think you can do that by reading books, learning, and playing as much as you can.
I play as a hobby - poker is not a career option and I don't even want it to be. I will say, however, that I am a successful low-limit player and I do pretty well in tournaments when I play seriously. I would take lessons, at a reasonable rate, if only to broaden my horizons, becuase I plan on playing higher limits when I become an attorney. (Still though, it will be a hobby!)
I could go on and on.
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