Regular rocket launcher has merit if you have fairly continuous access to healing, and want damage splash.
Liberty Launcher has speed, lowered ammunition... but I think it needs an upgrade also. Going to four rockets obviously doesn't work, because then it has no trade-off at all. With only three rockets, I wish the projectile speed were a little higher, but even that doesn't seem to fit.
Obviously, my ideal would be a Black Box with that +40% speed. At that point, I could never complain about three rockets, it would be such an amazing weapon.
I've seen a good use of the LL, by a Soldier much better than me. I can't do it, I'm not that aggressive, don't have the reflexes for it, rarely find an enemy to invade like that, and you can't heal yourself.