I started using .NET in the early 2000s. Ever since version .NET 3.5 (and even .NET 2.0 if we take a proper generics implementation into account), C# was dominating in the feature battle against its rival, yet wasn't advancing significantly in the product coverage due to its platform dependency.
Thus I was very excited to hear the news about plans to develop an open-sourced cross-platform .NET Core framework. We started using .NET Core in production from version 1.1, and a global decision to migrate the entire solution to .NET Core was made with the release of .NET Core 2.0. Now we have more than 100 .NET Core (micro)services running on Linux containers inside Kubernetes, using Kafka for reactive communications and a number of open-source relational and NoSQL storage engines.