In other words, the GM has to seriously contrive the situation in order to give the stun the 50% chance of success that is reasonable for a special ability like this..
Yes! Absolutely. The Monk is incredibly front loaded with abilities that are marginal. In my first 6 levels you get:
Unarmed Strike (Fair. Good flavor though.)
Flurry of Blows (Good)
Evasion (Good)
Exotic Weapons (Poor. Good flavor, bad play-balance. The +1 Short Sword goes to the Rogue.)
Stunning Attack (Poor. Generally ineffective.)
Deflect Arrows (Poor. Situational and ineffective.)
Still Mind (Horrible. +2 v. Enchantment School??)
Slow Fall 20ft (Poor. Situational and duplicated, I'm already taking Tumble.)
Purity of Body (Poor. Situational, depends on DM style.)
Slow Fall 30ft (Poor. Double duplicate. Whee, the Monk can fall farther than any other class.)
Improv Trip (Good)
Thats a lot of abilities compared to other classes, but who else gets so many medicore abilities? You get a bunch of good/fair abilites at 1st level and you wont get anything else good until 6th. Would I happily trade all of my 2nd-5th level abilities for one excellent ability like Sneak Attack? Yes, in a heartbeat.
Don't stick with the PHB! That's all you have to do.
I agree with that sentiment, but then its not clear what "Monk" means. How many supplements do I have to buy to make my "Monk" equally powered with the other characters? The Monk should be balanced (roughly) from the get-go, which he is currently not.
OTOH, I'm very hopeful about 3.5E - just moving the Ki Strike up to 4th level takes care of a lot of problems. It seems that the designers were aware of the shortcomings of the Monk and have made an effort to fix him up.