I've only used it at the field so far, but it's a pretty easy way to fly a "rails" pass. Even on a gusty wind day it does a solid job, far better than ATC. The only gotchas are input errors in glideslope and ship's speed. I forgot to set ship's speed to zero once, and wondered why the delta-path indicator was walking down the runway. You still have to take care of lineup, obviously. I also found it a little tough at first to un-learn the 3-part power correction mindset, but I was a 100% manual flyer on my previous fleet tour, even as a cruise-experienced JO. It's weird to push/pull on the stick until a centered ball and just "let go" until touchdown.
I'm a believer, at least until the jet starts to have degrades. I'm not ready to completely trust it and let go of manual ball flying skills yet, but I can see the writing on the wall, once the proper redundancy is in place. It'll be interesting to see what the fleet thoughts are on it when I re-CQ this summer.
For those currently in the fleet, what's the ball call with Magic Carpet engaged?