decreased build time, i assume. it takes a bit more micro to do it, but that's not a problem for pro players.
Yeah. With Warp Gates, you have to micro it more, but if you do it exactly right you can get ten or so seconds off every units build time. EDIT: The other, more obvious reason, that some people seem to forget, is that you can warp them to anywhere you have power. Whether this be the air unit protoss has that can transform into a mini pylon, proxy pylons, or expansions.
Basically, if you have a nexus warping in that's being attacked, but have a warp prism nearby, just warp-in some units, and the attacking force gets repelled easily.
The warpgate is a must for protoss players. I usually get my core around 17 and I research for warpgates the second I got it (and I boost it 2-3 times!).
With the Warp Gate you teleport units you buy. So each time you warp a zealot this costs you 100 minerals and take you 2 supply points off. If only we could teleport the units we have already. I can't teleport a Colossus for example.
Although warp gates may require to consistently create units for you to have a better macro, you can create any units in the gateway at any power sources. As long as the cool down on warp gates are done, you can create units in seconds so it's easier to gather forces far away from warp gates or defend. Proxy pylons are to stop wasting time for your units to walk all the way across the map when you can just create units around the pylon
Nice! Didnt know. shaving 10 seconds off is a big difference. Knowing how this works will save me a bunch of time and add to surprise.
I think warp gates are awesome - if you can micro. I mean how awesome is it to instantly create like ten units, if only it were not so expensive. Hmmm.