The law folder itself is durable and reliable. There’s a reason it has an NSN and is in use with at least a couple federal LE agencies.
However, there are a few potential issues some of which have already been addressed such as weight, complexity and the inability to fire more than one shot folded.
Another issue I’ve experienced is you need to account for the additional weight the plug for the back of the bolt carrier adds to the BCG.
I’ve run two guns with the law set up, an 11.5 inch pistol built and tuned by Sons Of Liberty Gun Works to work with the law folder and a 16” Colt 6920 with a carbine gas system. Both worked fine but both might be considered to be slightly over gassed.
I recently built a 10.5 inch upper using an expo/bloodline barrel. Carbine gas with a pin gauge verified Crane spec .070 gas port.
Suffice to say the 10.5) runs on every pistol an SBR lower I’ve tried it on except those with law folders. When doing the single shot lockback test, with this upper on law folder equipped lowers it consistently fails to lock back and exhibit other signs of being under-gassed which it does not exhibit with standard lowers.
The lowers I tried used buffers ranging in weight from H to H2. When I get some time I may try it with a lighter carbon buffer but for now that particular upper is a no -go with the LAW.
YMMV.