Quoted:
I have one.
I like it.
I eagerly awaited it since before I bought my REAL Scar. My thought was, after seeing how similar it was in apperance, to use it as a much cheaper training platform to offset the cost of .308.
When it was finally released, it was drastically different from the advertised prototype, and I was initially quite disappointed. After hearing about Glock's lawsuit against ISSC, I'm sure their lawyers mandated the change.
Having said all that, it's a fun little plinker.
While ISSC may be a different company from GSG, they are using many of the same parts. No doubt OEM'ed by GSG. Trigger, flash hider, bolt and "action", all are identical to the GSG-5. I went ahead and swapped the flash suppressor while showing a friend and if they are different, you're going to need one hell of a micrometer to prove it.
And that's where the little carbine fits, it's a Scar wannabe GSG-5. If you like the GSG-5 (like I do, I have two of them), you'll probably like the MK-22 (especially if you've got Scar in your blood) so long as you realize it's a toy and not a tactical weapon system. If you can't stand the GSG, stay away.
I've fired about 400 rounds through mine so far, and only had two stoppages, both of which were Remington cartridges that showed a heavy rim strike but didn't light off...ammo's fault, not rifle.
It's addictivly fun.
It is, however, not without it's faults. The stock is even cheaper feeling than the Scar's. It is loose and rattles (I solved this by taking it apart and wrapping the bearing surfaces with blue painters tape). The charging handle is poorly cast, though I like it's design better than FN's. It is rapidly moveable to SIX places on the bolt, three on a side, and doesn't require the rifle being disassembled to do so. Though I doubt SOCOM would accept a rifle whose charging handle is held in place by a spring and ball.
The barrel is GSG thin, with a faux shroud around it. Any suppressor is going to need a GSG-P style adapter. The stock iron sights are at best "barely adequate" (though novel, in that they have a "pistol" style sight while folded). Junk them and put on some cheap Magpuls. I threw on a Primary Arms Micro Aimpoint clone, and it's a wonderful combo. The pistol grip is one-piece molded to the lower receiver...no swapping it out for your favorite. The upper rails are held onto the aluminum receiver tube with tiny screws that have already backed out and required re-tightening...we'll see if this was a one time thing or re-occuring. Loc-tite would cure it regardless.
Despite all that, it's fun. It's accurate, and it's reliable. I popped my ACOG off the SCAR-17 and put it on more or less as a lark, and damned if it didn't hit point of aim at 100 yards without any adjustment. Same with the Aimpoint I had dialed in for the SCAR. That's kind of cool.
I bought it off Gunbroker for $440. I buy lots of guns, and frequently pay too much. $440 feels about $70 too much, but I wanted to be one of the first to buy it. I'm sure you will be able to pick them up in a few months for under $400. Hopefully, by then they'll have MK-22 Ver. 2.0 and will have addressed some of my (admittedly) nit-pick complaints. Of those complaints, the sloppy, cheap, airsoft-esque stock is by far the biggest.

Do you happen to have any pics of it? im curious to see what it looks like