I find that most guys look at porn/masturbation as an outlet for frustration or lack of self esteem in their own life. It is a cheap, quick thrill that satisfies them enough that they don't have to take a proactive step in finding a partner (SO) and moving on with a productive life.
Of course, that is all done subconsciously, most guys think of it as quick enjoyment, but I find that porn has negative aspects. I find that the only times that I have looked at porn were times where I was unsatisfied with my life, or frustrated with where I was in my life. And it is a losing battle, the more you feel despondent about your life, the more you turn to porn to give you that quick, cheap fix, and the more you don't deal with the real issues.
Yes, it is cheating. Cheating you out of cool relationships. Cheating you from viewing others in a manner that could build relationships (i.e. - viewing every pretty girl that passes your way as a girl you would like to have sex with and therefore being incapable of treating them as a human being). Fantasizing about a girl that other than physical beauty is probably really damaged emotionally means that you only regard physical beauty in relationships and therefore become calloused to mostly everything else. Building relationships with that mindset will eventually cheat you out of a great relationship with a girl that would make you a better person.
As for the learning aspect of porn, :roll:... there are plenty of books out there that talk about sex if you want to learn, but seriously, wouldn't you rather learn with someone that you can be vulnerable with and learn together through talking about it and experimenting, rather than a Cathode Ray Tube or LCD that puts up images that can't reciprocate those cheap thrills? (run-on, I know for you grammar nazis)