We are currently working on a social game app and proptech for a startup, both in .NET Core.
The game is Unity so C# on the app and .NET Core on the backend is nice to match up, common code.
The client on the proptech is Microsoft focused so they chose Azure/dotnet/C#/Xamarin.
Initially the proptech drawing/document app was on .NET Framework 4.6 and had the app running with Xamarin on Android + iOS when the app was to run on Android or iOS tablets/pads.
However, now the project uses Surface Books with touch/pen and Windows Ink so we went to .NET Core for UWP and that is the main app target now though it still runs on iOS/Android. Xamarin is quite nice for business apps that have to integrate to dotnet or any backend really. Lots of great developing and testing tools.
We have updated from .NET Core 1 to 2 to 2.1 and 2.2 and will be going to .NET Core 3 soon, by end of year.
The web app, apis and app are all .NET Core + Xamarin and it is nice. I have been doing .NET apps since 2000 along with Python, PHP and Node apps for interactive / promotional / game / drawing / rendering products and .NET Core is pretty clean and I love the nix implementations as well.
.NET Core 1 + updating to .NET Core 2 was a little rough reminiscent of the .NET 1.0 to .NET 1.1 and 2.0 initial start, lots of breaking changes, but .NET Core 3.0 is pretty solid and slowing down on massive changes, libraries and frameworks are almost all on it for what we use including IdentityServer4, SignalR, Xamarin (Standard) and more. The list of breaking changes is small this time [2].
There is the typical .NET base library depth that random deep errors you have to hunt down, and the thousands of libs/packages, but for the most part it has been not much more than speedbumps. .NET Core comes with lots of great security features for APIs/apps as well which helped us with compliance/security scans [1].
Now that .NET Core is pretty solid, and the linux/nix implementations and tools are far along, I expect with the ease of Azure, for Microsoft to really take some ground.
Microsoft ecosystem is a complete setup, from Visual Studio/Code to Azure to dotnet to Xamarin and UWP to Teams/Office and Surface Books with Windows Ink and even CI/github. They have retooled quite nicely, I left .NET in 2007-2010ish when developers took a backseat and they got it handed to them with mobile, but they are developer focused fully again.
Side note: I also love the Surface Book with the disconnecting screen and Windows Ink. My current machines are massive custom PC, massive Mac Pro (cheesegrater from 2013 that I love) and Macbook but seriously considering going Surface Book and probably just going to be updating/building on a Mac Mini for our Unity games instead of upping to the new cheese grater as it is the cost of a car or major home renovation project for the specs I want.
[1] https://docs.microsoft.com/en-us/aspnet/core/security/?view=...
[2] https://docs.microsoft.com/en-us/ef/core/what-is-new/ef-core...