I like the drawbacks of the old machinist crossbow (I still have one). The damn thing is absurdly heavy + it lowers your strength, effectively making it even heavier. I can't even use the damn bow on my own without getting encumbered, so I basically keep it in my bag and only use it when someone's in the party to provide me with bull's strength. On a strength-based character this wasn't an issue, but I'd say dexers (like the average rogue) had it pretty hard making room to use it, which made it worth it if you could make room.
What I'd like to see is more rare useful bows/x-bows like the one (can't remember the name off the top of my head) that gave a +1 AB and a +2 vs. undead, making it the ultimate weapon for slaying things like ancient mummies from a distance. I also recall one that gave +2 AB with a -4 dex and 50% arcane spell failure penalty.
I was hoping the devil-horn bows would at least do +2 vs. outsiders when they were released, since most outsiders have a +2 reduction.