You're doing the nike run are you. Are you confident of beating Paula?
Are you in need of commiseration now? I purposely pushed myself as hard as I could last night as I want to do a 10k run on sunday. My shin feels fine at the mo (touch wood). I'll probably trip over a chair and sprain my ankle now I've said that
Easier to measure speed. Easier to increase/reduce speed so very good for speed/interval training. Easier to run at a constant pace. Softer surface so better for knees, hips, ankles etc.
One tip for you though. If you run on a treadmill set the incline to 1.0 to replicate the wind resistance you'd get running outside