To everyone else - maybe I should have asked a better question, but it's quite clear to me now that people are in fact using this in production. That's great. My only question now is, what is Microsoft's strategy here? There's no money flow with .net core as far as I know, so why put in the effort?
Traditionally MS was laughed out of vast swaths of academia, research, and Enterprise solutions. Now, they're making ever more bank off of Azure, and want to get their products deeper into those markets where being Linux friendly, cross-platform, and all the rest are "must have" features. That's big money, and future growth.
At the same time: their current breed of engineers also struggles with some of the historic windows nonsense, and it's becoming ever less profitable to maintain. So it makes sense even for MS to transition a bit away from legacy MS.
SQL server runs on Linux now, MS hosts Kubernetes cluters and has Linux bundled in Windows, and Azure scaling is always cheaper when not paying OS licensing fees. MS stands to win a lot by having a relevant development platform, MS stands to win a lot being the tool provider of choice for cloud development, MS stands to win on cloud hosting and growth, and MS stands to win a lot with upselling to captive cloud customers (BI, BizTalk, OMS, Analytics, etc).
.Net Core is the free razor, everything else are the high-margin blades :)
Plus, Microsoft wants to get back in the game on mobile, so they need at least a platform, if not an OS. If they can put .NET reliably on top of Linux, Android, iOS, they can probably find ways to monetize that.