I play on my highschool's soccer team and we also use the 4-2-3-1. So far we're 6-1-0 so I think I can say that we employ the formation to a good effect. But there are some key differences between how we play it and how Chelsea plays it, obviously we aren't at the same level they are, but proportionally speaking I think we have something they don't.
Our team has two excellent holding midfielders, who can both distribute the ball as well as win it back. Chelsea has Mikel and Lampard as our first choice pivot players, and while both are adequate at the position (especially Mikel) I don't think that we have as good a set up as we could have. Lampard (who is my favorite player) does not have the mindset of a holding mid player, and as good as he is, he cannot and should not be in the pivot.
What we do need is a player to partner Mikel, who can both win the ball and distribute effectively. On my team we have a dedicated ball winner and short passer, and another player who can both win the ball as well as the dedicated ball winner but distribute it to a much greater effect. We haven't had one game so far when we haven't dominated the possession (the game we lost was similar to how Chelsea beat Barca) so I think we have the magic formula.
We need a player who can win the ball as well as Mikel and distribute it like Xavi, now I know this is a lot to ask for and given the market not entirely feasible, but I really think with a midfield of Mikel and another player who can win the ball/distribute it well we could be pretty much unplayable once everything gets ticking. Anyway that's just my take on how Chelsea could fix their midfield, albeit a pretty much wishful thinking take.
Tell me what you think!