I have one of these (and that same mag release and trigger!) with the concave nub and honestly I do like the unit. I've used pretty much every available hop chamber for the AAP bar the brand new TTI one which I simply haven't gotten around to buying yet. I think the Nexxspeed is the most universally applicable unit so far, ignoring the price; it adds functionality without any need for permanent alteration or any other trade off. If they made a cheaper version without all the funny high speed cuts it would a no brainer reccomendation imo.
You can also get these, as well as their hi-capa hop units, from hicapa hub in the UK. I fitted one of these in my AAP after I fitted their hicapa unit and I love it in both. Really nice bits of kit!
It would be interesting to know how this compares to the Loki. Obviously the Loki being a TDC people rave about the amount of hop and consistency you get, but this is far more user friendly in terms of adjusting in the field. Trying to decide if I get this or the Loki