Our glass shrimp just seem to hide in the shadows most of the time. You really have to look to find them.
We got 5 the other week, and today we had 3 hiding under the tree stump when we moved it. One died soon after we got it, and there may be a fourth hiding out somewhere.
I really haven't seen them do very much at all, so I can't really say they're a lot of fun, but an interesting addition while they last (and possibly a tasty treat for someone in the tank).