I have been working with Core all year, in fact started learning C# on Core RCs (which was a bit interesting..), but it was all on Windows. Finally the other day I just spun up a Ubuntu VM in Azure and got a sample Core app from my Win10 environment at home published up and running in a few hours, as step 1 on a small idea I have.
This coming from never having used Azure VMs before, and I was rusty with the SSHing / Linux as well. Not a lot of my friends would dig it, but as a relatively old timer I thought it was way cool. Microsoft code, running on Linux - definitely made my day.
Although, professionally I basically only do frontend work or node work. So javascript is pretty much what brings in the cash each month nowadays.
Right!? Half my co-workers still think I'm joking when I say C# or .NET
I still strictly develop C# on Linux, using JetBrains Project Rider and VS Code. I run production apps on Google Container Engine.
I'll test in Windows for cross platform apps using Visual Studio Community Edition from time to time. Never messed with Azure but I think they have some nice integrations with Visual Studio.
C# is a great language if you use the features well. Async/await and ThingOf<T> etc.
I know .NET has a bit of a bad reputation in some parts of the tech community but it's a great skill to have for stable job prospects. It doesn't matter if it's not cool. :)
Disclaimer: I wrote a book on .NET Core so I clearly have a vested interest in it doing well.
C# is a pleasure to work with. It's got generics and good support for asynchronous I/O. .NET Core is also very good, it's dead simple to spin up an API serving backend using .NET MVC.
Lastly, I think the community is great. I have jumped into a couple different projects - one is a MySQL driver and another is a MySQL implementation of the EntityFramework ORM. I was able to contribute after just a few weeks of working with C#. Microsoft seems very dedicated to continually improving the language as they develop in the open on GitHub and take user feedback.