My experience with it:
I was convinced to give it a try once when I was running low on feathers. I normally fletch with three. I adjusted my jig and fletched up a couple with two feathers. Sometimes they would fly well sometimes they wouldn't. Then I realized I was just shooting the same arrows with 1/3 less feather. So I refletched with two higher feathers this time, high enough to make up for the surface area I was loosing by only using two feathers. Things improved greatly.
Only problem was noisy flight. I could have gotten around this by using longer instead of higher feathers, but I brace my bows low. Also, I wouldn't have been able to get two fletchings from one feather if I went longer instead of higher.
So two fletch can work as well as any other configuration, you just have to use longer or higher fletching. At least that was my experience with it.