I picked up a Magpul MBUS Pro rear sight for my DD AR today. They've been out for a few months now but I had not seen any in the LGS' yet. Today I final found 'em. Just the rear though, they hadn't received any front sights yet.
There's a fairly long thread over on m4carbine.net and there were evidently a few hiccups in QC on the first run and quite a few rears went out that weren't up to snuff. Not unusable but not perfect. Magpul stepped up and took care of the issues with their usual excellent CS and identified and corrected the source of the problem.
The rear I got is perfect. Low profile, easy to flip up but the detent is very secure in both the up and down position. The windage adjustment is stiff but just stiff enough to allay any possibility of accidentally moving it, not so stiff that you need any tools.
As I said these things are low pro. Low enough to allow me to keep the precision aperture down and it still resides nicely under my magnifier. This something that I could not do with the gen 2 MBUS poly sights. And the other steel flip ups I looked at would not fit under the 3x at all.
What really surprised me was the price, $79.99 at one of my favorite LGS'.