My take on this deal is two-fold.
First, it's a good move for Milwaukee because Ellis is more of a certainty than Bogut, due to Bogut's injury issues. Additionally, Ellis is probably the replacement for Jennings, and probably a better player. Jennings is going to leave, and I don't think Milwaukee should keep him and Ellis. I think that would be a worse fit than Ellis/Curry.
Second, while it's a big gamble, if it works out, GS makes out like a bandit. Bogut is a legit C, and would make a very good frontcourt partner with Lee. The added benefit is obviously allowing Curry to finally be free from Ellis.
Overall, I'd say it's a fair trade. Milwaukee gets a little more roster certainty, but GS gets a possible home run if Bogut is healthy. GS took the bigger risk, but also stands to reap the bigger reward.