I have two suggestions on what I'd like to see more of in quests in general.
1. More options to use social skills when confronted with NPCs in the course of quests. Gatekeepers that can be bluffed into opening doors for you, minions who can be intimidated into telling you the secret password, captured prisoners who can be persuaded to guide you to the tyrant's bed chambers, etc. Ideally, I think every quest should have one potential use for each of the social skills. A few already have a use for persuade, in the questgiver's reward convo.
2. One alternate approach to doing each quest, focusing on the "opposing alignment" that the quest seems oriented to. Most of them are interesting to Lawful or Good, so a Chaotic or Evil alternative would be nice - and perhaps spark some interesting confict in parties trying to decide wether to attack all the hordes of desperate bandits in the name of Trom, or try to arrange a "peaceful" meeting with their leader under false pretenses, and stab him in the back.
Just my two cents. :P
Edit: I'm going to expand some on 2, after some discussion on IRC. I think that not only should each quest have two seperate completion methods, each one catering to two of the various alignment extremes, but the completion dialogues should also be split.
In other words, if you choose the L-G method of doing the quest, the completion dialogue which nets you the xp would let you choose so that you receive 1-5 points of either lawful or good alignment. Conversely, if you choose a nasty or chaotic way of finishing the quest, your choices will let you pick evil or chaos points.
One thing that this would help with is the much-discussed "paladins questing with evil" phenomenon. If they quest with evil people, these people will choose the evil methods of completing quests, and will drag the paladin's alignment down over time. On the other hand, if the paladin can continuously convince them to act more honorably, over time they may be able to actually redeem people.
Some of the flaws I can think of are that you could see-saw quest completion methods so that by going back and forth, everyone's alignment stays the same.
An effective way to counter that would be to vary the alignment shift based on how much you have. Characters closer to opposed ends would receive more of a shift than other characters - so an evil person who eats a baby might get 1 evil point. A neutral person might get 3 evil points, and a good person who eats a baby would get 5+ evil points.