We're one of the oldest PaaS's out there, with support for PHP/Ruby/node.js and both AWS and Azure. Earlier this year we launched a brand new user experience from the ground-up -- a new website and a completely new client-side interface. As a Frontend Engineer, you'd be working primarily on the latter.
The UI is written using angular.js served up by a lightweight node.js api proxy server. We use jasmin/protractor/selenium for our tests and only accept green builds via travis to be merged to master. Through our "eybot" on slackhq, we deploy stable code to production multiple times a day.
Take it for a spin at https://ui.engineyard.com if you want to see what you'd be getting into.
The UX engineering team at Engine Yard consists of 3 UI designers and 4 engineers (including myself). We're currently spread out across 8 timezones (Dublin through San Francisco), so experience working in a distributed team is key.
Great to have: