I watched a little video on react. I know slightly more than the nothing I did 10 minutes ago. It sounds like it integrates the js more into the html. Which could be more powerful especially for animation. I don't find Meteor's Blaze lacking though and suggest you give it a try. The react video said that it re-renders the whole ui after every change which sounds bad. Meteor updates only what you change.
I really like Meteor and would definitely use it again. Performance can be an issue but I think it's manageable. There are a few things lacking because it's new but it sounds like most are coming soon.