I recently bought a Kirby Morgan M-48 and although I only have a few dives on it, I am impressed with it.
In 34 degree water it has performed flawlessly with easy pod removal, replacement, de-watering, etc and I experienced no issues related to cold water icing etc. The mask uses a regular scuba style nose for equalizataion rather than a nose block (which is a plus in my opinion) and there is enough room to pinch your nose closed sucessfully even with 7mm gloves on.
It has a lot less positive bouyancy than an AGA which is a big plus as no weight kit is required.
It also has a great quick release on the harness that makes getting out of the mask very simple and very quick. Of course, I also discovered that you want to use the quick release rather than loosening the straps as you can't get a great angle on them with the mask on and there is a piece in the strap adjuster that is apparently rather fragile in well below freezing weather as I managed to break it. Using the quick release would prevent any problem, but I am ordering a couple extras adjusters for spares. On a positive note, a zip tie around both ends of the strap trailing from the adjuster worked fine as a field expedient repair and the second dive went off as scheduled.
In practice, I found you can leave either the left or right side straps adjusted and only snug up the other side after donning the mask. This would let you tape the ends of the straps on one side down to keep them from dangling and snagging monofilament etc.
The harness quick release comes with a neoprene cover/pad installed over it. This would be nice to have in warm water diving without a hood, but the padding gets in the way a bit when accessing the quick release with thick gloves on. So you'll want it for comfort if you don't have a hood (where you will also not have gloves making it a non-problem) but you may want to remove it if you are using a hood as you will not need the padding (but where you will also lose dexterity with gloves on and will benefit from it's removal).
The mask skirt curves in slightly along the cheek under the eye and this makes it hard to wear the mask seated on top of a hood without it leaking slightly. But it works very well with the mask sealing directly against your skin and the hood pulled up to or over the edges of the nask. (Some slight trimming of the hood material in the chin area eliminates any bunching under the mask in that area.) It would not be a good choice for diving in contaminated water, but a neck dam and helmet are preferable in that situation anyway.
You can also get it without the Kirby Morgan Superflow second stage which saves you money and lets you use your own regulator if you prefer. Care needs to be taken that the second stage does not contact the tilt valve that is used to drain the pod. The slightly accordian nature of the pod itself can cause some problems with exceptionally sensitive and easy breathing regulators. My D400 stuttered badly until the inhalation effort was cranked up a bit (from .7 to about 1.2 inches of water) and I ended up just going with my X650.
Visibility is the same as you would get from a regular scuba mask. It does not offer the fishbowl visibility of an AGA, but then it does not have all the reflection issues either.
The nice part about the M48 is that it allows you to switch to an alternate air source or a deco gas without having to have additional attachments, clutter and hoses running to the mask, without having to use a gas switching block, or without having to remove the mask and switch to a backup.
