.NET is much less a threat to Java today than it were 10 years ago. Today Windows is no longer the dominant platform, you have Scala for people wanting more advanced language features, you have Android and web applications are in general preferred over desktop applications. And if you are writing desktop applications then you need to take into account the Mac platform where .NET is at best a second class citizen.
And when it comes to IDE: I find IntelliJ far better than VS from nearly every standpoint - I simply don't understand your last remark.
As far as the IDE's, I've used both and can say that I vastly prefer Visual Studio paired with ReSharper (the R# in the previous comment). This is the first comment I've seen in a public forum, actually, that says that VS is not better than IntelliJ.
As for .NET, if it were a viable Linux server side VM, C# would be a very compelling language in comparison to any of the JVM languages. It blows Java out of the water, and even as a full time Scala developer, I'd have a hard time arguing against it vs Scala because the things I love about Scala come with so many things I hate.
Wrt. the other things; the way I see it .NET-support outside Windows has been "vapourware" since .NET's inception. It simply has not happened. In the beginning I thought this was MS's deliberate strategy but now the tables have turned and as a sinister business strategy it does not make sense anymore.
I have no more love for Oracle than I have for MS and I would love to see something as solid, cross-platform and performant as the JVM from MS but it just is not there.
don't need to wait much longer; it's already faster than nodejs for trivial benchmarks and getting better every day.
Unfortunately I did not understand the specific reasons he gave, but it had to do something with reification.
Still being crap in 2017, when the alternatives are good to great now, is dangerous, and Oracle's fear of alienating the masses of people who'll forever be two versions of Java behind is leaving the door open for Microsoft. I write games in C# in my free time, and between how great VS/R# is[1] and Microsoft supporting a CLR implementation I am inclined to trust more than Mono's on Linux and OS X, I'm excited at the prospect of being able to use .NET for server applications (no, no Windows Server for me, not now and not never) in the future.
[1] - IntelliJ comes close, but it does suffer, from a usability standpoint, from being cross-platform and having to compromise--I'd rather run a VM on my Mac to use VS than use IntelliJ, all things considered!