What is a hand crossbow? It's just a small version of a simple weapon, the light crossbow. IMHO, it's just plain goofy to say that a hand crossbow is an exotic weapon requiring a feat to use, regardless of it's rarity.
There is a reason that crossbows are simple weapons, rather than martial ones. They are pathetically simple to use. I own a hand crossbow and it requires virtually no skill or practice to hit something with it. Granted I can't put 10 bolts through the same hole on the piece of paper with it at 20 feet, but shooting it is even easier than the larger crossbows I've shot. Granted though, that was mainly because the range of my little hand crossbow is shorter so I didn't have as much error on guessing how high to aim.
I would venture to say that any illiterate peasant that isn't physically or mentally handicapped could learn to shoot it well in 5 minutes or less. If you want to keep it an exotic weapon for game balance, fine, just please don't claim it's because it's "hard to master" and/or "rare". I just find that incredibly hard to believe.