React recommends using stateless functional components because they allow more optimizations (which will be done in the future).
In an ideal world, most of your components would be stateless functions because in the future we’ll also be able to make performance optimizations specific to these components by avoiding unnecessary checks and memory allocations. This is the recommended pattern, when possible.
Yet the Meteor tutorial doesn’t use them at all.
Are there any plans to rewrite the tutorial with the style recommended by React ?