I've seen them but I'm not impressed by them. Ported / compensated barrels can be useful to some plinkers and are almost mandatory for IPSC type competitive shooters (guys who shoot heavily modified race guns). They help reduce muzzle flip and perceived recoil. The gases are directed upwards and that helps keep the gun down. -That said, they're a poor choice for anyone who wants his gun to pull double duty of plinker and self-defense due to the reasons cited by Devin/P88.
If this is a carry gun or self defense gun, you wouldn't want it ported because the flash will be directly in your line of sight. Also, if you practice with a ported gun and swap the barrels for when it becomes a self defense gun, you've put yourself at a disadvantage. You've practiced one thing when you're going to have to do another.
Personally speaking, I think compensated / ported handguns are a bane to new shooters. (I'm not saying that "sniperm1a" fits into that category.) I've been all around the country and I always see some loser behind the counter of a gun shop trying to convince a new shooter that he should buy a compensated pistol because it will reduce muzzle flip and perceived recoil. -They know the person is generally looking at something they can shoot at the range and use for self defense if they have to and they steer them wrong just to make a sale.