Forward guns which turn are ok, becasue they have at least a 15 degree arc. With the Lib one, even if you have it assigned to it's own weapon group it fires straight at 0 degrees, so you have to line up exactly, which is still guesswork in the calmest of battles.
The Lib Cruiser boomstick works really nicely against heavy caps. It's definately not useless. It just takes a little bit of getting used to. Once you can aim it (you aim it with the ship, not the crosshair) it's a really useful bit of kit. Hell, it works nicely against gunboats as well. Just gotta get really close.