From what I have read over the years crossbows were easy to learn/teach, time consuming to load and fairly inaccurate at range. The reload times and putting the x-bow as a simple weapon and bows at martial do a decent job at emulating that while keeping the fantasy flavor.
Historically x-bows were used almost solely from fortifications or in massed units. In one on one situations (like in most RPG situations) it would most often be a one-shot then throw it aside and prepare for melee. Yes, bows were often used from fortifications and in massed units but it was also a useful personal weapon. It could be fired more quickly so a user could cycle it more times before being forced into melee (or before that deer ran out of range).
From a FRPG perspective ... make that autoloading crossbow a character's signature weapon and have at it. I would also be willing to work with a player if they wanted to justify multishot and other feats if they really wanted to make the crossbow their 'thing'. It is not a game changer and if they are enjoying the game more we are all probably enjoying it more.
Personal note - almost no one uses crossbows in any game I have been in or GMd because of the reload time. There is the occasional hand crossbow used by the sneaky (and often poison using) types, but not much other than that. I also tend to halve the range increment of crossbows and allow them 20 range increments as well. The bolt just might make it 1200' ... but it is as likely to hit feathers first as it is to have the business end draw blood at that distance