Wow, I've had to deal with the issue of powergaming a LOT recently.
I've been running a D&D Epic-Level game, and I KNEW when I started it that the players involved should probably have been replaced with better roleplayers. I didn't listen to reason, though.
I've just recently ended up cancelling that game due to an excess of metagaming (using OOC knowledge in-character), a complete disregard for roleplaying in lieu of character advancement, and due to the ungrateful attitude of the players. Don't get me wrong... these guys are my friends, but they can't roleplay worth a nickel.
In my experience, it all comes down to how mentally/emotionally mature your players are (this of course also applies to your GM). Some of my players were in their mid-twenties and still possessed the mentality of your typical fourteen-year-old. Then again, I've known a fourteen-year-old who acts closer to twenty due to the maturity his life requires of him.
In the end, powergaming should NOT be the focus of a person's roleplaying experience. Sure, it's nice to have a powerful character. But roleplaying games are called such because the point of playing them is to be able to enjoy a fantasy where you are someone else. That being said, there is a place for powergamers... it's called Hackmaster by Steve Jackson games.
If your fantasy is compensating for something that you can't deal with in real life, then pick an appropriate roleplaying system and make sure your fellow players and the GM are intending on a powergame. There are also a gaggle of online/pc/console games that you can use to feel better about yourself as well.
Just remember, those who enjoy playing RPG's for their roleplaying opportunities and those who just want to powergame don't usually make a happy group when combined. Try to stick to your own and you should have fun either way!