'Grandy' (we can call him that now) is a 28-year-old All-Star centerfielder with a .272/.344/.484 (113 OPS+) career batting line. He's stolen 67 bases (with 17 CS), for an average of 16 per season.
He's a lefty that does not hit lefties well (.614 career OPS) and strikes out a lot (618 in 674 games).
His defense has declined (overall) the last four years (UZR's of 14.1, 12.9, -8.9, 1.6), so it's not a given that he plays center for the Yanks, who already have two quality centerfielders. If another outfielder is not brought on board, Joe Girardi will have to solve that problem (a nice one to have).
If Grandy plays center, we'll have one of the weakest hitting leftfielders in the game (in Melky/Garnder). If Grandy plays left, his offense will only be about average for the position. I'm of the opinion that, unless Damon/Bay/Holliday is signed, Grandy should play left, and center should remain a platoon of Melky and Gardner. Their defense has been better over the last two years than Grandy (.8 and 2.3 UZR for Melky, 15.4 for GGBG).
As for the free agents, they immediately get less leverage now that the Yanks have a plus (and relatively cheap) leftfielder. If Damon/Boras come down on their demands, would the Yanks go for a two-year, $20 million deal at this point? Are Holliday and Bay still in consideration? Is Matsui still in the picture? Is one of Melky/Gardner on the trading block now?
The lineup looks to be largely set for 2010. The Yanks have stated they want to keep the payroll below $200 million, and there are gaping holes in the starting rotation. Girardi has also mentioned that he wants to keep the DH spot open to give half-days off to A-Rod, Jeter and Posada. It doesn't look like any more money will be spent on position players. The next major move will almost certainly involve a pitcher.