Would reinstalling Lion help my performance issues?

Obviously something is wrong for Safari to be using over 1GB of memory by itself when I am not doing anything but playing a song from itunes and surfing 3 other tabs. I posted a question recently that said because I migrated from a snow leopard imac I might have PPC codes causing my problem but I don't think that is the case, as I had no programs other than sims 3 and a few programs on that computer, all of which migrated over fairly well, Osmos didn't but I'll figure that out later. I'm running a code to determine if PPC codes are causing these problems but what else might I do? This is a quad core i7 computer with a 7200rpm 500gb harddrive so it isn't underpowered in any way to simply running safari... At least I hope not because if it is I am switching back to windows=/

P.S. By poor performance I mean being very slow, getting multiple beachballs in the course of a day, requiring a LONG time to open programs (upwards of 45 seconds for simple programs such as itunes, sometimes), and very unsmooth operations such as switching from windowed to full screen app views not being smooth, etc.

Thanks