In plain language, ignoring D&D rules terminology, I'd describe them a cool combat moves.
In Bo9S they range from relatively tame and mundane stuff like disarming, fighting with two weapons or tripping, to magical and/or over the top like trampling enemies underfoot, shooting bolts of fire, turning incorporeal or killing with a single savage blow.
As a basic rule, you get to use each once per fight. While this can be said to have verisimilitude problems ("If I know how to trip people now, why don't I know it the next round?"), they're relatively easily handwaved away at the level of abstraction at which D&D works (it's not that you don't know, you're just looking for an opening), and in actual gameplay, it has the effect of encouraging/forcing you do be interesting and do different stuff rather than just say "OK, this guy is vulnerable to tripping, I just keep tripping him".
In Bo9S, the abilities have a distinct Oriental/anime/wuxia flavour, with names like Emerald Razor, Leaping Dragon Stance or (I'm not making this up

) Five-Shadow Creeping Ice Enervation Strike.
For inclusion into the core rules, I hope they tone down the wuxia names (as much as I enjoy them, it's not the flavour I want as the default) and that they make the more overtly magical abilities like lighting swords on fire or teleporting or becoming incorporeal only available to those who choose to pursue those path explicitly (feats to get access, PrCs... however this will work 4E). I don't want a swordsman just picking up the ability to shoot bolts of fire on the side, just because it was available.
That said, the mention of Bo9S as a sort of preview/trial run for 4E concepts is one of the strongest selling points for me so far.