Although if you're willing to change the rear gears an AOD can be an "okay" transmission, it'll never be a good transmission for cheap. They steal a lot more horsepower than a C4, and have a significant problem with their lockup torque converter. It is a mechanical setup, and gives you partial lockup in 3rd gear, with full lockup in Overdrive. Unfortunately, full-throttle shifts into 3rd and 4th will put things in a bind, and cause parts to either wear or shear to relieve the stress. It was a mediocre transmission for big soft shifting luxury cars, IMHO, and ill-suited to any performance application without a lot of work and expense.
I am not at all fond of the AOD's stock shift characteristics, the fact that it's about 50 lbs heavier than a C4, and I hate its fussy TV cable setup. It requires very careful calibration, and if the add on bits to your existing throttle setup don't work properly, it will burn up the transmission. To fix its shortcomings, typically the lockup converter must be sacrificed in favor of a one-piece input shaft, and a lot of upgrades that were included with the later 4R70W (the main parts generally fit inside an AOD just fine). The cost of these upgrades, done by a shop, is usually well over $2000.
All in all, I would rather have a C4 on any car over an AOD (given proper rear gearing for either). If you want an overdrive automatic, look towards the 4R70W. It is a descendant of the AOD, but gets rid of all the bad stuff, replacing its hydraulic guts with electronic actuators. It shifts asynchronously, which means it isn't dependent on multiple bits releasing and engaging at once to change gears. Instead, if you want first, it engages first. OD? BAM. And the lockup torque converter is actuated the same way. Typically, it is not programmed to lock the converter while in first gear, but can be programmed to engage or disengage any way you want, with most of the good controllers out there. It is much stronger and more reliable than a stock AOD, steals far less horsepower (comparable to a C4), and as long as you choose one built between '98-2001, has incredible longevity and power handling capability. V6 4R70Ws are still plentiful from those model years, and often need nothing at all but an aftermarket controller and rear gears to work perfectly for a long time, even if your car has a really potent engine.
Oh, and the "W" in 4R70W? Means "Wide" gearset. 1st and 2nd gears are a bit lower than a C4 or AOD, which means your car can really get up and move from a dead stop, making 3.73 rear gears feel more like 4.10s or so, without sacrificing mileage or top end capability at all.
Most people know that to use an overdrive transmission, you should change the rear gears to at least 3.50's or so. However, something that many people don't realize is that you should also use a lightweight (aluminum or carbon fiber) driveshaft if you put in an AOD or 4R70W. The reason for this is because the higher rotational speed of the driveshaft will cause significant driveline vibration. It can be hard on U-joints, as well as the tailshaft of the transmission and pinion bearings in your differential, not to mention being a constant annoying thrum while out on the highway doing 75+ mph. Since you will likely have to change out the driveshaft for a shorter one anyway, this is the time to invest a little more, and go with newer materials, which will not have the same harmonics. They also have resonant frequencies, but you'd have to probably be doing 300 mph for them to cause any trouble.