You will be slower outside in the beginning.  I had an increase in time and had to push myself a lot more than I did on a treadmill.  But I will say that once I started outside, I would much rather be in the elements.  Brings back that feeling of being a little more like a kid.

Being a little nervous is ok.  Might want to do just a mile or a mile and a half for the first couple times out there.  Let you're body adjust to the harder surface and changes in terrain.  Even an incline doesn't match the difference you can feel with your right and left foot hitting at even slight changes of elevation.  You'll probably be a little sore initially.  But if you expect that it won't be as much of a concern.

lol i know, like you i also began marathon training in early november, all outside!  Im in mass so this winter has been incredibly horrid. I too fear the roads at the moment!

Wow!   John425 you absolutely nailed it.  If that doesn't make you want to run outside, I don't know what would?   I think I will print your post and use it for motivation on those days that I don't feel like getting out there.  That being said, I can't wait for my long run tomorrow.  Every now and then I read something that strikes me as very profound, and your post is one of them.  Thanks for sharing.