Fangraphs just did their first UZR update of 2010. They changed the park effects, and now Bay's 2009 measures out at 1.9+, making him a 5 WAR player last year. It seemed pretty clear to me the large negative UZR he had under the former system must have been flukey, and Sam Page pointed out in an article how UZR had him as worse than Dewan and much worse than Total Zone. Errors and assists don't mean everything, we know, but given his putout rate, no errors, 15 assists and fact he isn't especially slow or appear to take really bad routes, it just didn't seem right that his UZR would be so bad, at least last year.
He is already at -1.2 UZR with the Mets (nice catch down the line last night however), and appears to be trying to justify his payday at the plate, but maybe his contract, at least the early years, isn't so bad. A year of UZR isn't enough to go on, but it does seem he was improving from the knee injury that hobbled him previously.