Carlos Gomez is the return. More later.
Later: Hardy is a guy that we'd all been hoping that the Mariners would make a play on this offseason to address the shortstop position, so it's a bit of a shame that he's been taken off the table so early and for what appears to be a fairly low price - one we doubtless could have paid. Gomez is a slightly below average centrefielder for league minimum, and the Brewers had top prospect Alcides Escobar waiting in the wings and a hole in CF with the departure of Mike Cameron, but I have a hard time thinking we couldn't have beaten that price.
In terms of money/talent, the deal makes a good amount of sense for both sides. The Twins get a big upgrade at shortstop, the Brewers deal from depth to cover a weak position (albeit not that well) for free, and have some more money to play with in free agency. As the return for a guy like Hardy, Gomez the talent is rather underwhelming, but the financial flexibility he provides is useful. Could/should the Brewers have gotten more for him? Yes. But they didn't, which is where this deal becomes weird from the Milwaukee side. They had an asset which had less value to them than to the rest of the league, but they sold him for his value to them rather than anyone else's, which is not the best trading strategy in the world.