Blizzard has been posting screenshots of the updated evolution choices for some of the basic units. Some of it we already are familiar with, but with this we have more details.
Corpser (roach): Enemies that die quickly after being attacked by a corpser will spawn 2 roachlings.
Vile (Roach): Slows enemy attack and movement speeds by 75%. (Heroic units by 20%)
Raptor (zergling) : Leaps over obstacles and onto targets. Jumps up and down cliffs. +2 damage.
Swarmling (zergling): Spawns 3 lings instead of 2. Faster build time: "almost instantly"
Splitter (baneling): Splits into 2 smaller "baneling spawn" after death. spawn deal less damage.
Hunter (baneling): Leaps over obstacles and onto targets. Jumps up and down cliffs.
I like the options available here much more to what tech options terran had in WoL. I can see situations where either strain will be useful, and being able to switch between the two depending on the type of mission I'm doing is going to be appreciated. Too many times in WoL i find myself thinking "you know what, if I only had X upgrade, tech, or mercenary instead of what I've chosen this mission would be a whole lot easier".