I've had a set of these on the bike now for over 2500km. They're good. Really good.
It hasn't been all plain sailing though, I got sent a set from Adam at Praxis and started out with the traditional rings but the chain kept dropping down on to the BB shell under load, a quick chat with Adam told me the rings were from a bad batch and another was sent across the pond express delivery. Thanks!
New rings mounted, all my chain drop problems dissappeared and the shifts were up to the standard of SRAM Red but still a little slower than I had hoped for having read the previous testimonials and their intenet blurb. Another chat with Adam revealed the rings are optimized for use with Shimano and that if I changed out the chain I'd notice the difference. He wasn't wrong and once I'd dropped on a DA chain and cassette the drivetrain noise was cut down to a quiet purr and the SRAM Red shifting was crisper than I'd ever found it before. Up shifting is the biggest improvement, it's noticeably quicker and sharper, even under load.
I've really got in to this testing. Whilst descending at about 45km my rear skewer snapped and wheel jumped out the dropouts, before I knew what was happening I was sliding down the road on my rear mech and the big ring, sparks flying out as I descended. The rings were kaput but took the abuse admirably and I managed to stay upright.
Back on to Praxis and they obligingly sent me a replacement set, this time in the clover leaf design. If anything this set is even stiffer than the traditional pattern and the look of them really suits the SRAM Red crank arms. I've been running these now for 2000km without any issue, in the worst of the British weather and with zero care taken, (I'm a very poor cleaner of bikes) they just won't give up.
As an upgrade I've found these to really make a noticeable difference to your front shifting on SRAM. Note that to get the best out of them though you really need to run them with a Shimano chain/cassette although I'm assured that the KMC is also a good pairing.
If their crank is anywhere near as good as their rings then it'll be a top product.