New write-ups in the states are not very detailed; but if you expand your search overseas there's more to see:
http://www.arms-cz.cz/novinky/clanky-testy-zkusenosti/180/The 557 looks like a handsome rifle, but it departs from controlled round feed to push feed. The extractor is more like an old Sako style, with a Remington-ish plunger ejector. There are pros and cons to this set-up; but comparing it to a 550 or BRNO 602 is apples to oranges.
I must admit, I look forward to seeing and handling the real thing soon.