I see there being two, somewhat distinct, categories of players: those with a realtime-first, focus (Meteor, Firebase and, now, dotCloud.js) and those that take more of a traditional REST-based approach (Parse, StackMob, Backlift, etc.).

The later have an easier time integrating into existing client-side frameworks (Backbone, Ember, Angular, etc), since those mostly seem to be built with a REST-based model in mind, but it will be interesting to see what patterns emerge to plug push-based updates into these pull-oriented systems. For starters, I suspect we'll need the client-side frameworks to clarify the distinction between the server and client state and the source of changes. Henrik Joreteg's talk at BackboneConf[1] was good overview of this and other problems they've run into.

[1]: https://speakerdeck.com/u/henrikjoreteg/p/real-world-realtim...

Flattering that you should compare us to them, but this is an early-stage experiment, and we're not quite sure how it'll play out yet!

CloudMine - https://cloudmine.me/ is similar, but more aimed at mobile...