It takes less than a day to port your number over. As a Project Fi customer I can tell you that 1) customer support is awesome 2) It feels like a VC-backed startup, they give you generous discounts for small issues 3) There are a few small issues, for example some fuck-up with wifi calling 4) It's terrible if you travel a lot 5) Its great if you travel a lot to places with networks that are Fi-partners.

What I really love is that they do true cash-back for unused data, not rollovers, etc.