I agree with Jayand, but also have not made light of anyone elses efforts either.
I feel that running longer distances on a treadmill is mentally tougher than running outdoors, whereas running outdoors is more physical.
One thing that does make me laugh though, the gym types who drive to the gym so they can then run on a treadmill. I do have a friend who drives 1.5 miles to the gym (3 miles round trip) so he can do a three mile treadmill run once he gets there!
Running outdoors can be very interesting, especially if running through nice countryside, although the view in the gym can be pretty interesting too
While I am drifting off thread, I may as well relate a recent treadmill incident to you.
I took a break in the afternoon from work, and popped into the local cake shop to load up on cream slices etc. All was going well and my hunger was growing, but just as I got back to my car I received a call on my mobile from my partner who had popped into the gym across the road. She had seen me getting my goodies while she was jogging on the treadmill (and looking out the window).
Getting caught taking a break is OK, but sneaking off for extra cakes got me into a lot of trouble!