Picketty -You're doing great!
I'd echo paul and say it's easier off the 'mill, I ran only indoors for ages, too embarrassed to go out- then one day, without much thought, I just go so hot and bored, I just got off, straight out the door and off I went!!
It felt weird at first, i didn't feel as if I was getting anywhere! - soon got used it though. Go for it I say!!
Word of warning - I came off the treadmill doing 30 mins plus of 8 minute miles with a burst of 7 min miles at the end, carried on doing 8min miles for up to 40 min runs, but made the mistake of slowing down in order to go further and never kept up my speed on shorter runs as well - result - I just did a 1/2 marathon in 2.5 hours was really pleased, but can't do faster than 11min miles!
PS make sure your shoes are good, it's probably more important on the road.
GOOD LUCK!!!!