It does have it's upside though from a training perspective. Outdoor is great for most of the time, but in really bad weather or when you need to create a specific workout when you do not have, say, a hill terrain or if you are just learning how to do intervals and training your body for a pace - it does serve a purpose, plus it has to be better on the joints than the road - especially for the more filled out folks who are getting started.
well, i still think running on a treadmill is different than normal running. i do know people who do workouts on treadmills, mainly tempo runs (treadmills here go 4:48 a mile). but not intervals. the treadmill does serve a purpose though. and is tons better than not running at all