I know this topic is a bit old now, but I would like to address some of the concerns made by the individuals here.
I am 21 years old, and like some here, I had Phimosis which led to discomfort during sex, but fortunately for me, not during masturbation or oral sex. I found that plenty of lube also did the trick, but it was annoying the hell out of me that I couldn't just be spontaneous with sex, and I would probably have to carry around lube with me if ever the moment arose. So, I decided to have a circumcision. I write this just 5 days after having one, and I am experiencing some of the worst pain I have ever felt in my life, I also have to point out that the procedure itself isn't as painless as some have mentioned. I look forward to the day I can get my penis back in working order but it won't be for another 3 weeks or so.
One more thing, my penis is bigger than it has ever been, due to swelling of course, this is causing most of the discomfort, and I would seriously advise buying some Y-fronts, pants, briefs, whatever you call them, they make life so much easier afterward.
I will say however, make sure you are 100% certain that you need this operation, it is not as straight forward as people would have you believe, but I have only heard good things about the end result, I am really looking forward to that. Remember, this is the point of view of a guy suffering the pain, so in a month I may look back and laugh