I'm going to post I made months ago about just this issue. You might find it interesting.
I have one and as said before it is indeed an improvement on the system, IMHO. I prefer to build my AR's but currently have 2 complete rifles, the KAC SR-15 E3 and a Noveske with 16.1 SS barrel. As a lefty I have even considered buying a $700.00 complete lower to put under my Noveske. The ambi controls are great. The mag release is superior to the Power, KAC, and Norgon units. The only ambi mag release offered as a retrofit that is close is the new Troy model, which really needs a thread of it's own.
As an experiment I built the closest thing to the KAC from the currently available parts for my wife. The idea was to see if I could duplicate what I had in the KAC. I ended up with a fantastic rifle for her. I used a stripped DD lower, parts kit, upper, auto bolt and carrier, carbine tube, spring, H buffer,and 16" pencil mid length. I added a Vltor stock, TD grip, magpul trigger guard, 13" Troy extreme rail and flip ups, Viking sling point, the afore mentioned ambi mag release, a Stag ambi safety, Noveske end plate, and a BCM gunfighter charging handle. For the trigger I went with the Geisselle SSA. As I had replaced the A2 for the TD on the KAC and added a BattleComp I also added a BattleComp on her rifle as well. Slings are both BFG's and both sport T-1's on Larue mounts.
The rifle compares well to the KAC. It weights 1/2 pound less but that's mostly barrel I suspect. The KAC's gas system does seem to run a little smoother with a little less sproing when cycling. The SSA is a little smoother, not by much though. The only problem is the dollars spent.
When it was all said and done I had $2040.00 in the KAC before adding the BattleComp and TD grip. $2230.00 all told with all shipping and transfer fees not counting the sling and T-1. About $2900.00 rolling.
For my rifle with all the same equipment added I ended up with $580.00 in the lower, $1200.00 in the upper for $1780.00. Add the sling, attachments, QD's, and T-1 and mount and I come up with $2450.00.
So for an apples to apples I ended up with $450.00 less in my top of the line lightweight middie. So is it worth the difference? To me it is. With the new Troy ambi mag catch I won't buy another lower but am glad I bought the one I did. It is the most advanced model of AR that I am aware of to date. I do with they offered it with a 14.5 or 14.7.