The weak point in the AR-180B design is the use of a plastic lower receiver along with the original front receiver pivot pin. A number of AR-180B owners have reported breaking the pivot area, and Armalite's manual for the AR-180B explicitly warns against overstressing this area (like, in letting the upper receiver pivot against the lower, striking it too hard).
There are some other problems too.
In addition, Armalite has not supported the AR-180B very well in terms of offering AWB-demise upgrades (but now are finally offering flash suppressors) and other features like chromed bores and folding stocks...
I have a relatively early AR-180B and, while it's a fun toy, I wouldn't pick it for anything serious. And, since you can get several AR-15 clones for less than an AR-180B (and the AR clones are quite robust and will stand up to misuse and abuse pretty well), why would you pick up an AR-180B?
Just my opinion, of course...
Forrest