Ironically enough, drop-bars are actually more comfortable than flat bars. You ride on them with less bend at the wrist than flat-bars and there are multiple positions to vary the load on your wrists. I see a lot of riders using too wide of bars, which causes you to ride with locked or inverted elbows, very bad for absorbing road shock. The results are sore wrists, arms, shoulders and necks in a short time. Don't do this:
http://upload.wikimedia.org/wikipedi...icerOnBike.jpg
Also, DO NOT squeeze the bars tightly with a deathgrip using your fingers, that's what causes improper positioning and pain. You want to place the place ALL of your upper-body weight passively through the heel of your palm on the spot of the bar that balances sliding off the top versus slipping off the back of the grip. The imaginary spot on your palm is where your arm-bones would extend out past your wrist. With your weight balanced on this spot, you can actually wiggle all your fingers and be relaxed. You can ride for hundreds of miles with your fingers loose.
Here's a good example, even if you have higher bars, you want to keep your elbows bent, with very little bend in the wrist... fingers loose:
http://www.giant-bicycles.com/_uploa...race_dirt5.jpg
http://www.singletracks.com/blog/wp-...oped-hand1.jpg