I don't have any experience with Gravity. I do have experience buying and selling bikes. You usually get what you pay for.
$400 might buy more "value" on Craigslist if you are familiar with bikes. Sounds like you have already done some research on the Gravity and its parts. That being said, I have had a blast in the past riding cheap bikes.
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I think its disgusting and terrible how people treat Lance Armstrong, especially after winning 7 Tour de France Titles while on drugs!
I can't even find my bike when I'm on drugs. -Willie N.