I have

  (Edited: )

been trying it out and it's been going really well. I don't hit quite as fast as Naniwa (I'm in gold) but I have managed to help secure victories this way. I have been having difficulty canceling a 3rd as my opponents never seem to get one, but when they do, this cancels it usually and if they don't, it's still good at harassing, and helps secure your second base which puts you on 2 bases vs a 2 base zerg which is awesome :3 in case you're wondering about the build...

  • 9 pylon scout (I like to leave this probe out for proxies later, but it's w/e)
  • 13 gate - cy core and zealot once gate finishes - immediately once cy core finishes get dat mamacore
  • 14 gas
  • 15 pylon
  • 21 (Naniwa cuts probes for expo I have difficulty with this and end up at about 25-27 supply here) Build warpgate (after the mamacore) once you're able, and plop down a nexus at the same time
  • 24-ish get a pylon at the front for your wall
  • 29/30 (at 100 gas) get a sentry
  • 31 (or at whatever time coincides with your target timing) get 3 gates on your wall and leave with your zealot, mamacore, and probe for proxies and warp in units to reinforce (Naniwa used only zealots as gas was low, but you can squeeze in a stalker or two)
Naniwa I think leaves his base at about 6:15-6:30 and usually arrives at his opponent at about 6:30-7:00 ish. I, personally, have been getting to my opponents base at about 6:50-7:30, which still works, but just not as well.
From there you can plop down 3 gasses and go Stargate or Robo or whatever you like and probably take a 3rd depending on your unit count at the end of the push, and how many units they have. Really easy to hold this 3rd if you save your zealots and core (but you have to pay attention to what he's going as well or a large group of banelings, etc. could destroy it).
As for what to do based on your scout, if you see him going expo first, or getting a reasonable timed pool (about 10+) go ahead with this build (At least in gold league, higher up, maybe only if they expo first or get a later pool). If he sends early lings off of a 10+ pool your core and single zealot should be able to hold the expo (with some slight micro try to save core energy though ^^). However; if you see an early pool (i.e. <9), you might want to play a little more defensive and perhaps hold off on your expo a little bit (but then again, perhaps not as a zealot and some probe micro should be able to beat it and you should be able to eventually get the mamacore out in which case GG). I haven't been vs such an early pool as of yet, but those are my suggestions.
Kill the cute, pesky zergies,
Seren ^^ 
P.S. try to save enough energy for a recall, but you can use a timewarp to help trap or hold off units