There are a few posts about them here already. Not a hugely popular pedal, most likely due to marketing or lack there of. They are a super nice pedal. Absolutely nothing in common feel wise to the Axis. Closer to the Pearl, but way simpler. Just a straight forward minimalist great pedal. For direct drives, you could consider the Mapex Falcon as well. That one comes in chain, but can be converted to strap and direct as well, so it gives you some options.
It's a great pedal if you like direct drive. Keep in mind that Yamaha may be coming out with a new pedal line soon. If that happens, these models will surely go down in price (although they're probably already less expensive than the others you listed).