I can't tell you how awesome my local running store is; not only do they offer free fittings, classes, and water for local runners, but they are always willing to sponsor any local events -and I live near ATL, which has a huge running market. In addition, when I cracked the face of my Garmin three months after I purchased it, they replaced it with no problems and no receipt!
I've been tempted by these Internet deals, but I feel like that would be cheating on my running store. My advice would be to stick with a business like that, especially since I know if something goes wrong, they got my back.