I've been playing around with the longbow recently, and so far I love it. I only have 6PD, but I can still take people out on average in 2-3 hits if they have full health. If they've taken any damage or if they have low armor I often get one hit kills. Midway through the battle when everyone's taken a few hits, the longbow absolutely shines: I end up one-shotting almost everything that moves, regardless of armor, since pierce damage is so deadly to armor.
The nice thing about the longbow is you can severely damage ANY target on the battlefield, regardless of armor. See that guy in plate? in chainmail? Fire away, if you hit you're going to do some massive damage compared to most bows.
Also, the longbow's insane projectile speed means your arrows will get to their target very quickly, making them harder for the enemy to dodge. the downside is you can't keep an arrow nocked for very long like other bows, so you have to predict when to draw the bow.
I'd say try out the longbow for a while, it takes some time to get used to it. It's a very slow, patient kind of bow. In my opinion it is the most rewarding of all the bows, however. (Also I hear it might be getting a buff?)
http://forum.c-rpg.net/index.php/topic,4540.msg83494.html#msg83494