The out-of-the-box reactivity make it the best framework to be used for application. Other tools might take so much to get this reactivity as a standard

The best feature of Meteor is hands down the triple-binding it offers by default. Where other frameworks have two-way binding between the views and their controllers (in this case html files and JS logic), Meteor takes this one step further and allows you to bind views, controllers, and datastores. Essentially this boils down to saving database queries to a variable. In practice you might have an information store. In Meteor you can say "var x = my_datastore.fetch_contents()" This variable is now bound between the controller and the mongo database in Meteor such that they are always in sync. Further, if you make x editable by the client through the view Meteor handles a lot of basic state saving to keep all three in sync.

The ability to fast prototype apps with server connection is cool.