Both True Shot and Crossbow Expertise are broke (the damage is not applied, see
here). Even if the crossbow skill worked, bows are faster and tend to do more damage in a given amount of time. Also, there is one unique, potentially powerful bow in the game as a quest reward, but only random drops or trading for crossbows.
Poisoned Arrow, Splitting Arrow and Explosive Arrow seem to be good, from what I have read.
