My point of view is that somebody using 1.x should be able to switch to 1.x.y with a rather strong trust that that's not going to break their application (while moving to 1.x+1 might require some more review and testing).
No, x.y+1 is supposed to be strictly better than x.y; if we need to release x.y+1.1 that means we screwed up, and I'd like not having to release 1.9.1 in a couple of months.
Now, we may come to the conclusion that that's too hard, that the x.y releases are really more like release candidates, and that we should expect people to move from x.y.1 to x.y+1.1. If that's where we're headed, I'd rather just have explicit release candidates for e.g. Wine to test with before we make the x.y releases.
We may also/instead come to the conclusion that the roughly three months between releases is too long, and that we'd like to get targetted fixes for specific applications out sooner than that. That would be where regular x.y.z releases come in.
I don't think we're quite there yet for either of those scenarios, but that's my current thinking.