Exahusts seem to be one of the hottest topic for 2011 (how hot? ask marekk or ringo for an estimate).
Design path taken by teams are different from each other, for positioning and shape of the pipes.
Some have kept a rounded pipe shape for the exit (Mercedes, Renault), others have gone for more stretched, rectangular shapes (Ferrari, RedBull). Toro Rosso and McLaren (in testing) have, or have tried, very thin and elongated exhaust exits: slit exits.
I think this could be a potential direction of evolution for exhausts exploiting, because thinner but wider exhausts could blow closer to the boundary layer, and could interact more exatensively with surfaces. I see potential for exploitnig coanda effect too.
Most probably from an engine point of view they are not an advantage, but I think that for aerodynamics slit exahusts could be more powerful than circular, or elliptical pipes.
What do you think?