Great answer there edp773. Only two things I'd add... even the cheapest Trek will feel nicer than the wal-mart bike in every way. It will shift better, run more smoothly, more reliable, etc...... and at this stage you probably wouldn't be able to pick the difference performance-wise between the cheaper and more expensive Treks, so don't let the marketing hype or bike shop sales people convince you that you 'need' the more expensive bike because you definitely don't at this stage.