Meteor Is Just A Toy
I use it. It works. That is nearly all I have to say. It looks ugly, feels wrong but thanks to some third party libraries it is at a point that I can justify using it.
On the frontend there is just no real alternative. Since most browsers fully support it, at least if you follow some basic rules, there is no real reason for not using it.
I tried node.js. I wrote two applications and I have a basic feeling how it works and what you can do with it. Language aside, node.js is not bad. You can do some cool stuff and it looks stable enough. Some companies even proved that it is production ready.
Since it is new and no one has some real experience we should look at everything we have. I tried those demo applications and looked at the code but did not write something by myself. The basic trick is that you get real time, synchronized updates for everyone and everything for free. I click on a button and you see a counter go up or something is added to a table.
If you ever wrote something like this by yourself you know how painful it is and that every bit of code that takes away some work from you is a present you should accept.
But this is the point where my critique starts. Beside realtime stuff and integrated deployment tools there is nothing new. If you do not need this it is likely that you find yourself writing node.js applications. Another framework, another toolchain, another library just means another layer of potential problems.
And even if I think their demo is pretty cool: not every application needs real time communication. Really, even if it is the new joker in web development bullshit-marketing-bingo you use to win.
Another thing I find a bit troublesome is that they currently expose the whole database to the frontend. I believe I do not have to say much more about this, especially after you have read the next point.
There is currently no authorization or authentification system. It is planed but not implemented. So you basically expose your whole database to every client without any way to add some security. Since they already announced that this will change you should not take this too serious.
And last but not least they are not really near 1.0. And they announced that the API will change. So you can build an application that will work with the current version of Meteor. After they release an update you want or need you likely find yourself rewriting some parts of your application instead of implementing new features.
Just A Toy
In its current state Meteor is just a toy. I do not see it being used in a real world application. Not yet. It lacks some basic functionality you (IMHO) just need. But when it is mature and fixed most of the stuff they are already working on we will have to take a serious look for some projects.