That said, I dont know what your roster looks like, so I'm not sure I would've passed up Gordon.
At 3B I have Rolen, Braun, Fields, Marte and Campbell, basicaly 3 of the top 4 or 5 3B prospects and an aging Rolen. And OF is definitely my weekest position as far as players who have had success in the majors and adding McCutchen gives me another impact prospect there (along with Maybin, Bruce, Chris Young, Pie, Markakis and Sizemore). I'm ok at SS (Lugo, Hardy, Felipe Lopez and Brignac), and it's nice to have security there.
Keeping the 1st round pick was a HUGE factor in making the deal. I might even get Longoria, while he's no Gordon, he's another solid 3B prospect.