I wouldn't write a commercial, production application with anything less than 1.0. In fact, I wouldn't write a commercial, production application with anything less than a 2.1. ;-)
The cost of supporting these projects early is that you're likely to be rebuilding anyway a year from now, but I think that's implicit in the version number.
In my opinion, the biggest risks of Meteor are this:
1. It hitched its wagon for now to mongo, so you'll be doing the same. If you happen to believe that schemaless isn't all its cracked up to be, that's a real problem in production.
2. You're picking both a client and a server. Sure, you can strip apart DPP or Blaze, but why would you? If you're not wanting to benefit from Meteor's reactivity, you can just use any server+client combo and, say, a websocket connection or something like React.js for UI components.
3. Meteor has a financial incentive to round up as many devs into their own ecosystem (atmosphere?). They want to sell you servers, services, et cetera, like Heroku does. Nothing wrong with that, but it's something to be aware of.
For all the debate about JavaScript frameworks, I have Backbone code I wrote a relatively long time ago and it's still durable and not being refactored. I can't say the same for Ember or Angular code in my experience or observation. Backbone as a library is lightweight enough that I create the framework, following good design principles, that's best for a given application. Your mileage may vary.
It's not to say the people at Meteor aren't a great bunch of people who really love what they're making. Meteor does some interesting things and I think hopes to solve some complex problems. Hope they get there. I'd love to see Meteor mature and become a tool to build bigger things (UI components I agree would be a welcome step).