For guys that have this holster, is this holster the best thing out there right now with locking retention? also is the als worth it? I don't plan on going hands on with anyone but climbing obstacles is common. Does anyone have an alternative to this mid ride/leg strap setup?

IMO the ALS is the best form of active retention. There are a few up-and-coming competitors but the old hood systems work as a secondary mechanism at best.

I know Blackhawk has their T series but I haven't had any hands-on experience with it so I can't speak as to its efficacy.

Is there a specific problem with the 639x you're facing, or are you trying to find an alternative because your gun/light/etc. combo won't work with one?

I have had all types of kydex holster over the years but I am trying to find a better holster if there is one as I transition to mid ride from high ride.

Just be aware that with the 6390 the mounting holes on the back sit lower that other models so this pushes your grip higher. I was issued a 7 series that I used to run on a mid-ride UBL. With the transition to 6390's it required a low-ride UBL to drop the grip to about the same height.

I have been buying gear for a long time. When I started out I was always looking for that thing that was just better than what everyone else was using, but experience taught me that when something is the "standard" there is a darn good reason for it and now I discount something that is used by the majority of folks.

The Safariland 6390 isn't perfect, but I have made it perfect for me by matching to a True North Concepts Modular Holster System and modifying with a Nub Mod, light portal, and new barrel end piece to accommodate my comp.  I'm pretty damn happy with it now and I trust it, because so many people the world over have trusted the ALS for years.