Four years, $61 million. As Woj notes here, it effectively ends Brooklyn's pursuit of Dwight Howard.
A few things had to fall into place for them to get Howard such as finding a team to take Kris Humphries in a sign-and-trade, so it's understandable that they'd want to hold on to the starting centre they already have. However, it's a lot of money to give someone coming off major injuries and with a couple of glaring weaknesses for a big man. Lopez has talent, he's fairly good offensively, a strong free throw shooter for his position and he can block shots. However, his rebounding leaves much to be desired, not even topping five per game per 36 minutes last year and sitting at just six per game in a full season the year before last.
His first couple of years were more respectable as he was up over eight rebounds per game and if he dedicated himself more to cleaning up on the boards he'd probably be a 20 and 10 player in the right situation. As it stands, with Williams, Johnson and Wallace on the team he should probably at least be posting Joakim Noah-type numbers, a double-double along the lines of a 12 and 10. That wouldn't be too bad, indeed the Bulls are paying Noah a similar amount of money for that kind of production. Lopez doesn't have the same defense, rebounding and hustle though, meaning the Nets are overpaying for an offensive player who isn't going to get enough touches to do what he actually does well.