Originally Posted by adrien
Depends how serious you are, but most cross bikes will do well in road races, up to about 85-90% of what a good road bike with similar weight / componentry can cover. If you're in it for the sport of it and not necessarily for the winning gear, you'll do fine. And you'll be able to switch out a wheelset and go off the raod for some real fun. The other advantage is that your bike will be a little tougher than the typical roady.
I use a Kona JTS this way, and have two wheelsets -- one with 38 semi-knobbies for trail / dirt / commuting use and another with slick 25s for the road rides. All you need to convert back and forth is 20-30 mins with the bike to switch the wheels, check brakes and shifting, take off any fenders etc.
Ditto on using a JTS with 2 wheelsets - I also have a Trek Madone. JTS is noticebly different, but its sure a fast bike when I switch to the 23s. Big difference between the 2 is in climbing hills. TM flies, and I feel safer taking curves on downhills at higher speeds, but I really like that JTS.