Is loss of accuracy an issue when you install a post ban legal brake such as Wilsons, Cav-compm or Kurts?  I am really interested in Kurts A2 brake but I was wondering if installing one would affect accuracy. Does anyone know?

Assuming you want to install a brake for its true purpose of preventing muzzle climb which facilitates faster second shots then the brake may actually make you shoot better overall.  However if you are looking for benchrest state of the art accuracy then the brake will probably cost you a little bit.  I have 2 Bushy M4's one with the mini Y comp and the other has a slotted A3 brake from Gunsmoke and for my purposes they don't hurt accuracy and do make follow up shots much faster to get on the target.  Hope this helps.

Brakes will in general, spread the flash out and increase noise. they do improve accuracy. The Bush MAster AK-74 style muzzle brake for the mini-14 got my groups at 100 yards down to 1.5 inches.... too much flash at night and in indoor ranges(I work in one)
-Chuck

I would think brakes would generally tend to degrade slowfire benchrest-type accuracy, but there are a lot of variables.

If brakes do hurt accuracy, then those that are the least symmetrical probably hurt it the most. Say like where the bullet passes close to a flat solid surface on the bottom, while there is a big open hole on the top. Since the pressurized gases surpass the velocity of the bullet after it "uncorks" the muzzle, it seems reasonable that you wouldn't want an unbalanced situation with them bouncing off a surface on one side and not bouncing off a surface on the opposite side.

But in practice, it might well be that a particular brake might, by its mass, just happen to tune the vibrations of a particular barrel and so actually improve accuracy much more than it hurts it.