Official React support - woohoo! I've been using React and Meteor together to build a desktop web app for quantified self, and I have to say, the combination is magnificent for productivity. The app is 90% JS and a little CSS, and reactively updates with no extra code. MongoDB and server logic is separated from the client-side view rendering, so if I wanted to make it a thin client and remotely host the computations…
React and Meteor work really well together. It's a lot less painful than trying to use Flux with an API backend. Super productive. Can't wait for SQL support and for them to FINALLY fix the build speed.