I started out with a BMX bike as a youngster, then got a road bike when I was about 13. In college I got my first mountain bike, and rode mountain bikes exclusively until a few year ago. When I realized I was riding my mtn bike on the road for half of my miles, I decided to get a road bike. Now I'm 50/40/10 between mountain, road, and miscellaneous bikes like my cruiser and "homeless" bike. I don't understand how people limit themselves to just one type of cycling. I think you're missing out on a lot of fun , and, the skills you develop with one type of cycling transfers to the other.