I still don't know whether to call it a 3-5-2 or a 3-4-3, but whatever it is, it seems to be working pretty well after a game and a half. For a couple of reasons.
One is just the overall talent on United's roster. The team easily has 12 players who are worthy of starting every match, and that number will be 13 when Olsen is healthy. And it's also good that several of these potential starters (Burch, McTavish, Quaranta) are flexible enough to play in a couple different positions.
Another reason is the speed at the back. The main reason DC did not use the 3-5-2 much last year I think was that Boswell was too slow to be the lone center defender. But we talked earlier about how the newly acquired speed of los Gonzalos will allow Marc Burch and Bryan Namoff to get forward more. Well now the team is eliminating that transition and just going with 3 backs to begin with.
I think there's a point that got lost in the excitement of the 2-1 "victory" on Wednesday. We know that two substitutes Dyachenko and Niell scored the two goals, but there was a third substitute too: Marc Burch. And his insertion may have made a bigger impact than we really saw. This seemed at the time like a strange move. Bringing in a defender Burch for a forward Quaranta? But Burch played the left wide midfield role, and pushed Fred more into the middle. When Burch came in, right away he fired off two left-footed crosses. If Fred was still on the left, he probably would have tried to cut and dribble those balls inside. So a true left winger instead of a left winger who likes playing in the middle forced Pachuca to spread out a bit more on defense, once they learned that they had to respect Burchie's crossing ability. Also, Fred then had more freedom to roam the field, which may have helped allow him to set up Niell's goal.
So I like the new formation, mostly because of the options it brings. But what I don't want to see is DC United reverting back to using a 3-5-2 permanently for every game, like they did in 2006 and like the Revolution have been doing for years. This can be a risky formation, especially when one of the back 3 go forward, which Namoff, Peralta, and Martinez all have a tendency to do. But I think it's very valuable to the team in certain situations, like when you're down 2 goals in an aggregate series (Pachuca match), or when you're playing well defensively but keep losing possession in the midfield (Toronto match). So with DC's current roster, it's great that the team will have the ability to work well in different formations, and will definitely keep opposing teams on their toes, not knowing what lineup to expect.