Although i agree that Capello could've made an effort to switch to a more fluid and attacking formation, and tried employing a fantasista, i think the fact that he wanted to stick to the 4-4-2 meant that Vieira was really the best purchase in terms of a upgrade, we could get.
And now with Mutu in the fold, i think our offensive option upfront are going to improve immensely, as Del Piero will have a more dynamic player to potentially link up with, and with Vieira, we will be able to start attacking from the middle. Sure, he doesn't have the vision or passing range of an archetypical playmaker that's because he's a DM, but he's still a good passer of the ball, and he does contribute well to build up play. This in tandem with Nedved's hopeful resurgence, plus Emerson's and Camo's continuing good form, and we have a mighty fine midfield.
Vieira is still the player that was the focal point in midfield of Arsenal's free flowing and offensive football. There's no reason why we couldn't conceivably be that for us as well. Although whether Capello's tactics will allow this, only time will tell.