I've been using C# in Godot for all of my latest projects of the last ~year and have had absolutely no issues at all. Most of the docs these days have a "GDScript/C#" tab selection, and the intellisense support is so good that I rarely even have to check.
Now, I did already know the Godot API quite well when I started using C# so that contributes. But I haven't found it to be a second-class citizen at all, and in fact allows me to use features that I wouldn't have been able to in GDScript (native event handling, offloading to native data structures for computation rather than using the Godot API for them, nuget packages, and so on). I can also use eg Jetbrains DotTrace to profile code in much more detail than GDScript, and edit and launch my game code from an IDE without ever opening the editor.
You can also opt to use the dotnet-core compiler instead of the bundled Mono one these days which allows you to use some more modern features.
The only clunky thing I've found is that trying to use a native C# data type in a Godot Node object causes marshalling errors, but I'm pretty sure that would apply to nearly any Mono game engine and that Unity has similar issues (having to wrap things in MonoBehaviours etc- it's been a while so this may be inaccurate). The simple workaround is just to use the Godot API for things that are in the scene tree, and native types when you need to compute stuff with better performance.
I'm curious as to what actually felt rough to you in C#?
