What are some alternatives?
When comparing Umbler and Heroku, you can also consider the following products
Microsoft Azure - Windows Azure and SQL Azure enable you to build, host and scale applications in Microsoft datacenters.
DigitalOcean - Simplifying cloud hosting. Deploy an SSD cloud server in 55 seconds.
OpenShift - OpenShift gives you all the tools you need to develop, host and scale your apps in the public or private cloud. Get started today.
Google App Engine - A powerful platform to build web and mobile apps that scale automatically.
Vultr - VULTR Global Cloud Hosting - Brilliantly Fast SSD VPS Cloud Servers. 100% KVM Virtualization
Nanobox - The ideal platform for developers. Focus on code, not config.