Y'know, I like the paladin's code. My favourite paladin was a depressed guy, who was upset because he still had his paladin's powers, despite all of the "questionable" (in his mind at least - he was protecting prostitutes, gamblers, and street people from thugs, by dealing with the thugs as nonviolently as possible) activities he had undertaken. The fact that he still had his powers made him question his deity's commitment to goodness.
Fun character, that.
I really like the Grey Guard, a PrC in COmplete Scoundrel that lets the paladin player "bend" his paladin's code a little bit. I think it expands upon the flavour of the paladin's code.
All that being said, I think the paladin is a bit underbalanced at times. In our group, he doesn't have the pure combat potential as the goliath fighter, although the paladin's use of cure wands has kept the party alive. The Code has never got in the way of the character, though - I wouldn't really even call it a "weakness", because a properly played character will never come up against it. Compare this to some of the flaws in other classes - the barbarians fatigue after raging, for instance.