I have two Mag-na-port customs, a Charter Arms Bulldog "Backpacker" .44spl (one of a run of 250 done by Mag-na-port back in the late 70's) and a 3" S&W M29 that has received the full Mag-na-port treatment - porting, action, grip frame reduction, etc., plus some other work by a local 'smith. Both shoot extremely well, with a marked reduction in recoil, and have excellent actions. Noise and flash are not increased as much as redirected so they may seem worse, though the flash is more noticeable with the .44spl than the .44mag.
I also have an Automag V in .50AE that's ported from the factory. I've never shot any other guns in .50AE for comparison but I can tell you that muzzle jump isn't bad, the recoil comes back more than up. It's pretty brutal (and I'm not recoil shy), I can only imagine what it would be like without the porting.
So, IMO porting has it's place, as long as you know what you're getting into and what to expect as far as advantages and disadvantages. Also, I'd like to say that for all the talk about muzzle flash and and night vision, I've trained in low light and darkness with a number of different weapons and have never found it to be that big an issue, especially with modern ammunition.
