I've used Meteor. I thought it was a good system. It didn't have offline capability, at least not back when I used it. It really needed to be connected to work. But conceptually, yes, it had a very similar system.
Yeah, faced the scaling challenges. What was recommended was using the "methods" which was basically RPC to fetch the data, rather than using the PubSub data syncing. Meteor maintained a full copy of what data each client had in memory, so this made it use a lot of RAM, and it did some kind of diffing for these on each update to only send the required updates over the wire, so this made it have high CPU utilisation. I had to move the chat portion of my app over to SocketIO which scaled wonderfully, but the DX was not quite as nice.
Rails and Phoenix are doing something similar (kind of) these days, and those seem to scale better, you just move all the data heavy lifting to the server and do almost nothing on the client.
