My main love for biking is on my mountain bike. I have recently been doing some road training and commuting to work on my old hardtail. My question is this... Will I notice a huge difference riding a road bike instead of my hardtail w/ slicks? Will I be able to maintain higher average speeds with the same effort? Before I drop $800 or so on a new road bike, I want to make sure it will be worth it. Any input is greatly appreciated.