I have the Large version of the Pro Harness. It's built well. Things I like about it:
-The bino strap connections no longer hold the shoulder straps to the case like the originals did
-waterproof/resistant case without a fly/cover (haven't used yet in heavy precip, but handled light drizzle fine)
-Binos are fully enclosed in the case, so no junk gets in when it's closed up.
-bigger side pockets with good stretch to hold smaller gear
-ability to add attachments to the bottom (I use the ammo holder), the original didn't have this
Things I maybe don't like so much:
-Harder to retrieve binos from the case as the back comes up so high. This is the biggest downside to the Pros in my view. Probably helps with keeping junk/moisture out of the case though.
-Case is much larger than my 10x42 SLCs demensions. They include spacers to raise your glass if needed (I use 2 of them), but there's still a lot of side-to-side space so the SLCs aren't "snug" in the case. I may shim the side as well if this ends up bugging me. It hasn't in any practical way so far.
-Front zippered pocket is almost useless. Maybe could fit your Driver's license in it? Oh well.
-It is bulkier in size than the original overall. Covers more of your chest real-estate.
My biggest issues with the original KUIU harness:
-lots of debris always got in the case and all over my glass
-fighting to find the shoulder straps after disconnecting binos to put them on a tripod
-the case itself sagging down my chest when the binos were removed from them and being used
-the side pouches were really tight and it was difficult to put useful items in them
-carrying the mini rain-fly for them as they weren't water proof, not a massive deal but, I often forgot it at home/camp
I think the Pro version addresses all these issues fairly well. They aren't perfect, but I'll take the good with the not-as-good for now. I must say, these impressions are based off of 1 hunt so take this for what it's worth. I also don't have any past experience with harnesses other than the KUIU original bino harness that I've been using for the last 4 years so I can't speak to how it may compare to other company's options.