Particularly with modern brake hoods, riding with your hands on the hoods is a very ergonomic, comfortable position (assuming the bike fits you, etc.).
Drop bars are nice because they typically give you at least four distinct hand positions:
Riding on the "tops" is when you have your hands on the part of the bar near the stem; this position lets you sit most upright. It's a position that is often to used to take a bit of a break on the bike, and that's okay.
You can ride with your hands near the hoods, but not all the way to them; this allows you to turn your wrists in the more natural "handshake" position, and you sit a bit more upright than you do when your hands are all the way out to the hoods. How comfortable this position is depends quite a bit on the exact shape of the handlebars, and how they're angled. A nice level "shelf" is desirable for comfort, in other words the bar flows right into the hoods, giving a large amount of relatively flat surface.
Riding with your hands on the brake hoods. Again, with modern brake hoods this a very ergonomic position for your hands. You can easily brake from here, the hoods are designed for this. Shift from here, too, if using integrated shifter/brake levers. And it's important to relax your arms as much as possible. A big mistake a lot of folks make is leaning on their arms so much they get numb hands, a sore neck, shoulders, etc.
Riding in the "drops" gives you better aerodynamics, and can also give you better leverage to really mash the pedals in some situations. When riding into the wind, this position is especially helpful. If you're going to have drop bars on your bike, in my opinion you should be able to comfortably ride in the drops for at least a few minutes at a time without being uncomfortable. Proper bike fit and good riding form are often the keys in being able to do this.
Last edited by well biked; 01-13-09 at 11:17 PM.