Thanks for your feedback, Jim!
We'll take your suggestions under advisement.
As for an upper limit to iPads, there shouldn't be. The only limit is the server, and that's on the cloud so it's quite scaleable. That said, the way the iPads currently respond to changes might not scale realistically to a really huge number of concurrent updates. As in, it might take a while for each client to catchup to many updates / sec for a long period of time.