Track drops:
Pros: sexy, if you sprint out of the saddle your forearm won't hit the upper part of the bar or curve
Cons: Only two riding positions, one of which is relatively uncomfortable for long rides and unsuitable for city riding, the other of which is a little too narrow for climbing leverage, and you lose control. People call it leverage, but that's a bit of a misuse of term. Oh, and mounting brakes can be a bother, most look terrible, except for cyclocross levers near the stem

Road drops: Same as track drops, except brake levers generally do better and thus afford more hand positions, but hoods make the bars bulkier, and they're often wide to begin with.. kinda lame on a fixed gear, as you've found.

Time Trial/Tri Bullhorns (as opposed to flip and chop jobs):
Pros: Many hand positions, if they're long enough, you can get into a nice aero position while still being sort-of high up. Internal cable routing on some models. Brake mounting is sexy and effective with "reverse" levers. Great for climbing, I've found.
Cons: Look a little funny if they're really long, and if they don't have a "drop" to the horn parts. And they often look out of place on old steel bikes, except for the nitto models.

Flip and Chops:
Pros: economical (usually), great upright hand positions for city riding, ample flats for comfortable positions, generally accepted for use on any road bike, you can cut 'em like you like.. also great for climbing
Cons: Not quite as many hand positions as other road-oriented bars, have to do your own handiwork, brake mouting can be dicey (again, cyclocross lever or reverse lever if you can get it to fit), no real aero position (really, most of these have a completely different feel than time trial bullhorns, because those have a drop and long horn section, and these usually are angled up and have a short horn section). Most older road bars are very narrow for bigger people, but some people (me included) like narrow bars.. give me 35 and I'd be happy.

Flat bars and risers:
Pros: really wide or really narrow if you want.. I guess you can do barspins, but no one cares.
Cons: everyone will hate you if you put these on a road bike, especially with those damn neon or oury grips (there is a reason you people find them so difficult to install). Few hand positions, none of which are very effective for city riding. Did I mention your whole bike will suddenly look like ****? Please don't put these on.. I'd give anything not to see another road bike with flats or risers. They scream "I like fast bikes, but I can't handle the resultant body position. And I may be brain-damaged".

EDIT: If I see anyone riding a bike like this, I will not speak to you. I'm serious, folks.

(sorry to the guy who posted this in the riser fan club thread)