So, big question: why should I run a pre-release Team Foundation Server update in production? Isn’t it risky? And what about support in case things go wrong?
The biggest reason why you’d want to do that is because you really want to allow your users to enjoy the very latest features of the platform.
For example now we have TFS 2015 Update 2 available as a Release Candidate 1, and you might really want to deploy it because it includes the new Release Management features (for the record, I am 
). You can also have reasons related to performance problems, very specific bugs, etc. but usually features are the culprit.
The quality bar is pretty high. I ran many non-RTM releases in production and I hit very few problems or blockers, with live loads and real users’ expectations.
The second best thing about running a go-live pre-release is, oddly enough, support in case things go south. If you have a production issue with a pre-release of TFS, you get some kind of special attentions and for free!
That is because you are providing some very useful feedback from production scenarios, collaborating to increase the overall quality even more.
And eventually – if you upgrade to a pre-release you are still on the official upgrade path, so you can move off it without problems when the RTM is out.
There is a trick though – you must run only go-live releases in production. It might sound obvious, but think about it for a second: it is a pre-release, but if it carries the go-live license it means the quality is high enough to be trusted in production. Different story if we look at CTPs or betas – they often aren’t go-live supported and they are meant only as an evaluation version for future upgrades.