Im a fan of AUS-8 steel but damn thats the best steel they use, thats why im not into SOG knives.
well, the steel on the vulcan is seki city vg10, wich is good. however, the vulcan costs almost 100 dollars. you can buy a spyderco with seki city japanese vg10 for about half the price.
for the extra money i paid for the vulcan mini, i expect zero play. the play is minor, i just dont like any play because i have bought cheap 20 dollar folders that locked up tight, so i really expect a 100 dollar folder to be able to lock up as well.
also i agree with phil. there are plenty of knives that have play that are still good. i had a spyderco endura that hada bit of play, so i used it as my work knife. i put the knife through hell, thinking it was inferior because of the play, and yet it never failed and withstood incredible punishment. i work in construction.