I don't think it's having much effect.
For starters it's only applicable on homes that complete before March 31, 2013. In Vancouver, we sell presales very well for the most part so anything with a completion date in that area is likely already sold out or close to.
In general though, a fair amount of my buyers for Presales are first time buyers. I've found first time buyers get really excited about having brand new, and the drawn out timeline gives them more time to prepare for being a homeowner. Things like being able to pick colour schemes, upgrades, specific suites within a building they like, seems to appeal to first time buyers.
Also they tend to be scared of condo issues and special assessments, so having a new home warranty puts them at ease a bit.