Do you want to be talked out of or in to one?
If you do the math you'll find the 16" .40 has more energy at 100 yards than a 4" 9 mm pistol at the muzzle. You'll also find that it's fairly anemic compared to a 6" barrel .357.
I think it's fairly useless except in rather narrow circumstances. I would not buy a non-folding semi auto pistol caliber carbine (like the Ruger, Marlin, etc.), and I'm not sure the folding feature is worth much (folded, it isn't that much smaller than an AR with the pins popped), but my .40 sub2k isn't for sale either. I'd suggest a .357 lever gun is more practical if you want a pistol caliber carbine.
The only time mine has really come in handy is when some friends asked me to house-sit and I wanted to ride my motorcycle to their place.... Toss it in a saddlebag along with some clothes and have something a little better than a pistol or H&R single-shot.
It is fun as a plinker.
Good luck finding one. I've seen an RFB, I've seen a KSG, but I haven't seen a sub2k...not since the one I bought 5 years ago.