My main problem was using the shifters and brakes. In fact I still cannot use them, I have the extra brake levers installed on the top of the bar. Just cannot get used to not being able to get 3 fingers around the brake lever. Also the narrower handlebars make the front wheel seem twitchy- which it wasn't, just coming off a wide flat handlebar plus bar ends.

However I gained 6 km/hr switching to a road bike- could keep up with my friends, and realised it wasn't me.... it was the weight of the bike.