I too recently made the transition from MTB to road (tho I still MTB once in awhile). The biggest difference to me was that my road bike handled soooo differently. It's a lot more touchy than my big heavy mountain bike is. But, it goes SOOOO much faster! I can ride for longer and go farther faster than I ever did on my mountain bike. And all the extra hand positions are nice. You'll find your position on the road bike is pretty different from the mountain bike, you're more bent over. Also big for me was that my MTB brakes can stop me on a dime, but my road bike brakes at best just slow me down!

Next you'll be going for clipless pedals!

Have fun!

--K