Yes, they do indeed work. When a fish is on its side, it's under serious stress. Most people will immediately fizz a bass, but really you should try to keep them upright first. Often they'll equalize themselves that way without the need to fizz them. The hard part is keeping them upright for as long as 20 mins.
As Big-O mentioned, a partition in the livewell will help solve this problem, but even then you still need to constantly monitor the bass. The weight clips solve this problem and work quite well. But they're not a cure-all. They are designed to help the bass regain his equilibrium. When it works, it's good for the fish because you won't need to stab them and puncture their air bladder.
Key thing to remember here: if the bass hasn't equalized himself within 20 mins, then you'll need to fizz 'em. If the fish is under that kind of stress for more than 20 mins, they can get brain damage. So don't just clip and forget about them; keep checking to see if they need fizzing.
