Zendesk user reviews
Zendesk - a well-known cloud-hosted support software "for better customer service". Features Email/social integration, KB-module, mobile apps, community forums (optional) etc.
Nice app, but it can be really slow at times, especially the admin/agent area! Other than this annoying sluggishness - its nice and easy to use. Also, Zendesk is widely used, so other apps offer tons of integration features (if you need it), like, Hipchat or IFFTT, out of the box.