Considering there's only one turret, and the rest of the guns are locked forward, I can't imagine it being too terribly lethal in most hands. But the whole point of the shuttle was that it could at least hold its own in a scuffle, which we could easily use to our advantage in missions. It's not like they're known to have high production numbers and you're likely to see a fleet of them in one place. Considering it would almost definitely be following FREDed paths most of the time, and not zooming around with the other fighters, it really shouldn't be too hard to use. I'm trying to think of the common uses for a Lambda in a mission, and trying to see how having 8 vs 2 or 4 forward firing batteries is going to cause any significant difficulty, and I'm just drawing a blank. Even the rear turret won't be too difficult to avoid, considering it has a fairly narrow cone of fire, as far as I can tell.
But, I'm an eternal optimist, and as I won't be a primary FREDder, I'd like to entertain opinions from the other staff too.