More specifically the 6390. 

6378 model owner here*.  It's well designed ergonomically, the thumb release falls right where expected and it seems resistant to being jammed by tiny bits of gravel and unlike the SERPA pulling on the pistol first doesn't seem to lock it up.  The ALS 'hood guard' seems to help, but my holster is also left-handed so likely not many are practiced with gun grabs from that smaller part of the population.

* same basic design but sold without the 'hood guard' which I subsequently added.

versus

Yes, I have the level one ALS model designed to fit the Leupold DPP.

It works well, the optic cover is a nice addition, and the fit is right on. It's typical safariland quality.

Did you have to modify the ALS system?