It isn't a deal breaker for me either. I just think it's neat that you can buy 1 mag and use them in different guns. That's sure to help some with logistics.
Matter of fact, I'd kinda like to have a hipoint carbine with the ati stock that looks similar to the storm, but I'm not sure they're still making those anymore.
I would totally go for a 10mm upper that would share mags with my 29..... It would be too much damn 10mm reloading but I bet it would make a mean pistol cartridge upper
The Kriss mags are factory Glock 21 mags with the extension to 30 round capacity. Both the 13 round factory mags and the extended 30 rounders will function 100% in either the pistol or the carbine...