I'll by the first pair of any new shoe (or for that matter upgrade) in a local running shop. Accepting that most will then offer a 10 - 15% discount for club runners I'll probably go back for more pairs of shoes but have occasionally ordered online.
Basically, I'm a bit of an impaitent sod and for the sake of £5 or so I'd rather walk out of a shop there and then with what I want.