Just sensor replacements for phantom obstacles. Nearly all the problems I've read about have been simple adjustments or small component replacements, or dings from opening them in tight spaces. While they are complex, they have not required a bunch of total replacements.
Inside a garage they may default to a low enough opening that it could be hard to get in, or you could hit your head on the door. That's one reason why they don't hit stuff in tight spaces anymore.
With the phantom obstacle problem, my wife was so used to overriding the FWD that she tried to open it full inside a very low parking garage. It hit a big pipe in the ceiling and put a tiny scratch in the paint. So operator error can be a problem.
I think the FWD reliability concern is way overblown, based only on complexity, not experience. Of course we only have a few years of anecdotal data so far, so who knows how much trouble they'll be in 20 years.