I actually like the trade for both sides. Golden State wants to become a more well rounded team. They get that with a very good true center in Bogut and an all around solid player in Stephen Jackson. This gives GS a likely starting 5 of Stephen Curry, Klay Thompson, Stephen Jackson, David Lee, and Andrew Bogut. That's a solid foundation.
For Milwaukee, they get rid of a disgruntled Jackson who doesn't want to be there and in return they get easily the best overall player in the deal, Monta Ellis. They also get the youngest player in the deal in Ekpe Udoh. I actually think the back court of Jennings and Ellis is perfect for the Bucks because now Jennings doesn't have to shoulder the scoring load (like he has the last couple years). He can focus on what he does best, which is be a true point guard while Ellis does the heavy scoring. Both guys will be better playing together.