Read up a lot on the Sub2000 once -- don't have one but I think they can be taken seriously, with caveats. Wouldn't expect one to stand up to year in, year out range sessions and high round count courses.

That said, with basic care and limited use, I'd expect one to hold up well and be dependable as a personal defense carbine if needed, with the bonus of extreme portability should one desire that.

The aftermarket is getting fairly robust for them, too.

But by and large, it's a fun gun in terms of hard use. For most any serious application the Sub2000 is marketed for, an AR will outshine it and I'd say the latter is the way to go for fighting carbines, if the shooter's willing to put in the time to learn and perfect its use.

But for the casual home defense enthusiast who wants something basic, compatible with their handgun for an HD set-up that they'll shoot enough to be proficient with, then clean and have at hand but otherwise more or less ignore, a Sub and caliber/magazine sharing handgun isn't a bad combo.