Braid is EXCELLENT for casting, but only for fixed spool reels. I use it on a small fixed spool reel in the summer for spinning, but I have used it with good results for bottom fishing for bass from beaches. The good points about braid is the very high breaking strain ratio to the very low diameter of the line. Also there is no stretch in the line, so contact with bites is imediate.
However, there are a couple of points to remember to get the best results :
Fixed spool reel only (if using it for casting) ; fine on a multiplier for boat fishing.
Don't fill the spool as full as you would with mono..slack loops will result in knots, which are IMPOSIBLE to untangle.
Don't use in very windy conditions.....especialy a side wind.
Don't strike too hard on a 'bite' remember there is no stretch, so you don't want to pull the hook out.
Also I always steep the spool in warm water to remove all the salt from it after a fishing sesion. As someone has pointed out it is very expensive, but if you follow the above points it will last you for a few seasons.
Good luck