I had a lot of excitement for the C# repl window, then I tried it and quickly lost interest. Partly because I currently use a tool like LinqPad and really like it, and also because I was expecting the C# Repl window to automatically load (or at least give a command to load) the current solution into scope with all the Classes and related Libraries ready to go.
It would have made exploring a code base a delight. Not to mention the fact that you could use the repl while you are actively developing to experiment your ideas and then copy and paste the ones that work back into your solution. This is my current workflow with Linqpad for Linq Queries. I thought the C# REPL would be the ultimate tool for this workflow