Experience is only useful if it's good experience. McCain's experience consists of toeing the Bush line for at least the past 8 years, engaging in questionable ethical practices, cheating on his wife, covering up for his wife, warmongering, voting against the troops, supporting torture, and lying about the other side's political positions. Given that kind of experience, I'll take the new guy any day of the week.

ETA: It doesn't come down just to experience, anyway, IMO, because the policy differences between McCain and Obama are vast. Oceans apart. And McCain, on nearly every single issue, IMO, is dead wrong.