rules wise, it's all formations. so if you're expecting to play in tournaments it doesn't really do you much good (unless the tourney allows everything). fluff wise i don't know, i haven't read through it yet.
they're mostly formations that use lictors or genestealers and have specific special rules (better infiltrate and cover) for specific terrain types. there's a cool lictor assassin formation and an intersting gargoyle + spore mine formation.
for $15 it's not really worth the money unless you're a real die hard fan, or the formation become a regular fixture in tournaments.
