Really? I'd actually be interested to hear more about Sharepoint. My experience with it is getting to be awhile ago, and it was VERY unpleasant. What does it do for developers now?
All in all though, it is a very solid offering from MS that nobody really talks about. One of the main pain points from the past is that everyone thought it was a CMS when really it was a document management system. Now it actually can be both. There is a talk on YouTube from the unveiling of 2013 that is well worth a watch (although it is over an hour long)
.net, Azure and javascript are supported and documented best, but you can use any language and run SharePoint apps on any platform.