Bananna plugs: worth it?

I was considering adding them, but there must be some loss involved? It would seem bare wires are the best route to avoid any loss or signal degredation?
Also, what about soldering bare wire ends prior to adding to the amp or speakers. Is that a good idea or not?

Thanks guys, after reading everything, I see they are useful in situations that call for tight instals and no room to attatch bare wires in binding posts.
I have room to move in my setup, and used one of my craftsman sockets to tighten them, not over-tight. I think I'll just stick with what works now.
One thing I did do, was use de-oxit in my ports, cable ends and speaker connects. It really did clean them up quite a bit. Great stuff.