Gerald's numbers on NJ were quite good. His defense looks to have improved, and he had the best plus/minus on the team.
Granted it's hard to take too much away from performance on a team that awful, but he is at least a legitimate NBA player now.
And, he could have a role on the Celtics as instant offense off the bench.
I have no idea how to assess his value, though. How much do people think he's looking for?