I've been messing around with Day9s ZvZ build and I'm not the biggest fan of it. Playing defensive feels awful, especially since you're in the dark most of the time.
I've found that playing offensively with Roach/Speedling in ZvZ is pretty effective. Open 14 gas 14 pool Speedling leaving a single drone in gas, Overlord 15, get a Queen and spawn four sets of lings. Then, expand on 21 and drop a Roach Warren straight after. Pressure forwards towards your opponents ramp and push up when Speed finishes at the 5 minute mark to see what he's doing.
From there, squeeze out a few drones, depending on how many units he builds, and then pressure like crazy with Roach/Ling.
If he techs too quickly, he dies. If he drones too heavily, he dies. If he produces a lot of units, well, then it comes down to micro and your ability to inject.
On super big maps like Shakura's, I'm not sure how well this style of play will fare (I haven't played it enough to form a conclusion yet), but on the small to medium maps, it's pretty awesome.