I have a couple I picked up for a good price here on the EE - wish I had the money at the time to get all of them he had. They match up with the regular black anodized lowers really well. They would be great for a GM Hydramatic clone.
The only thing I hate about them and the NDS uppers is the forge codes, I know this doesn't bother many people but it does look a little off if you are wanting to build a completely original build. They have the splintered A for Anchor Harvey forge mark under the rear sight where a Colts would have the letters C H. And NDS receivers actually say NDS in a different font style then the originals.
The only quality issue I have seen on my 2 is 1 of them has a little bit of a surface blemish where the forge marking is. Like a tiny grind mark in that area, it isn't very noticeable but I am not very picky on surface finish. I just did a battlefield pick up look to it with some scotch brite pads and a little banging/scratching with some screws/nuts I had laying around. It turned out quite nice and I plan to do many more like this since I prefer the been there done that look. I really like how the black anodized receivers look after they are aged like this.
As for fit and function, everything is as smooth as any other upper I have used. At first they were a little gritty inside since it had a new finish but after a little bit of use it smoothed out to be like all my others. I recommend them if you want this style upper. But I also see plenty of used ones show up in the EE. And while you may not get one the first day you look, I would say if you checked every couple hours you would find one within a few days-week for a good price.
Brownells now also offers the true A1 uppers in black if you decide you want to do an A1 with the forward assist after this one. Everyone acts like the black is a big deal, and while it would be nice to have Colt grey available, I really enjoy doing the GM Hydramatic builds.