There are two schools of thought at my field, with the guys who fly 3D:
1) NO. It interferes with flight! I can't get it to release and allow me to fly properly!
2) When it's dialed in, I can do things that I couldn't do before, or I had to REALLY fight the controls to get it to fly the way it flies with AS3X on.
That last bit came from what everyone in our club considers to be the best pilot in the club. The guy's gone to Joe Nall and numerous other invitational events to fly 3D, and he makes it just look SO effortless. I've seen him take an Apprentice and fly it, inverted, 2 inches off the tarmac, and be cool as a cucumber.

If he's saying it makes 3D flight EASIER, I'll take him at his word.
That said...You have to get it dialed in. How, on that, I'm not sure. I'd have to go to Spektrum and really read up on how to make adjustments to AS3X flight controllers, but if it can improve your flight, it might very well be worth it if you can get it programmed properly.