While most of the improvements of Mesh Army Knife will be described in the sections for the user interface panels, here are some improvements that are not directly visible in the user interface:

Options are saved:
Some of the options and spinners are saved so that they are set to the values you last used if you restart max: Weld Treshold, Target Weld Picking range, Use UV correction for Target weld (see below), Extrude uses local or averaged normal, UV mapping offset (see below).
The settings are stored in the file meshak2.cfg in your 3ds max "plugcfg" directory in your user configuration dir.

Better navigation in command modes:
If your'e in a command mode like edge divide or vertex paint, you sure know that the navigation around your object really sucks, if its a big object. That's because the viewports rotates around the center of the whole object. And if it's a big object, the center may be far away, so that turning around can be terribly complicated. Detaching is one possible solution, but it's circumstantial too. So I decided to go another way: The last subobject, which you worked on (e.g. in edge divide the last divided edge) is selected and you turn around this subobject selection as the center. You will be surprised how much this little feature will boost up your navigation speed.
The negative effect of this is that you lose your previous subobject selection, and that the selected edges/faces etc. may be optically disturbing. While max doesn't support a better navigation, it seems a good improvement to me though.
The other flaw is that this doesn't work in every situation; for example it can't be used in the vertex paint feature, because you are not in a subobject mode in that case - and so you can't rotate around a subobject. All in all, it's just a workaround; it would be a quite better thing, if discreet could implement a rotation mode, where you rotate around your last click on the object, which I already suggested to them.

Hidden Edges unselectable in Objects with "Edges Only"-flag
Hidden edges are not selectable anymore in "Edges Only"-mode. This makes it very much easier to select only the visible edges, which is sometimes very useful, e.g. if you want to create splines from an objects edges. simply switch the "Edges only"-flag off, if you want to select hidden edges. You may switch off this behaviour to the original Edit Mesh behaviour in the settings dialog.

Fixed Edit Mesh mapping bug:
Ever had a destroyed mapping on a mesh when using the Edit Mesh Modifier?
Try out the following simple steps:

1. Create a plane consisting of 4 faces. Put a (standard with diffuse color bitmap)
    material and an UV mapping on it.
2. Put an Edit Mesh modifier onto the plane.
3. Delete face #1. It is important that you delete face #1. If you e.g. would delete
    face #4, the bug wouldn't occur.
4. Turn one edge.
5.  Move one vertex. The mapping is destroyed.

Fixed Vertex Color bug:
Sometimes the vertex colors are destroyed. You may also easily reproduce this bug:

1. Create a box, 10x10x10 segs
2. Switch vertex color for this box to "on"
3. Put an Edit Mesh Modifier onto the box.
4. Go to vertex subobject mode and select some vertices (about 100 or more)
5. Switch the vertex color for this vertices to black.
6. Switch it to blue.
7. Switch it to green.
8. Move one vertex. The vertex colors are destroyed.

The destruction occurs also, if you save the file or make a copy of the object, or if you select some other vertices that intersect with the previous vertices. Try yourself. This bug MIGHT be the reason for the sometimes completely destroyed and unrecoverable vertex colors (this thing, that you paint and paint, and always the colors are destroyed again, even if you collapse the object, copy it etc.) But I am not completely sure if this is the reason for this bug also.

"Attach List" without extreme memory consumption:
The "Attach List" Operator of the original Edit Mesh Modifier allocates ridiculously giant amounts of memory and tends to crash your system, even with 2 gigs of ram and 2 gigs swap, if you attach many objects. This has been improved in Mesh AK. Still it's a bit slow, but this might also be improved in further versions.