I totally misread this and, after a glance, thought that it was a nice cross-language RPC library. Like many fiddly bits, whipping up a quick protocol is simple (and I've built one that I like), but I'd be happier to use one that everyone is helping build/maintain/document...

But I was wrong... This is a service... or something. The web page suggests library, but the pricing page suggests service. Color me confused.

[An aside: these Pusher, PubSub, whatever businesses exhibit very little in the way of barriers-to-entry. As the price to replicate the service falls (as smart folks think "pay for that? I just make it into a gem/pip/AMI!" and crush the implementation costs), I'm curious how these business will survive. See Engine Yard...]