You really don't need to use any new features to get the benefit of improvements in many cases, because the standard library is updated to use them. So things l

You really don't need to use any new features to get the benefit of improvements in many cases, because the standard library is updated to use them. So things like string and array operations just get faster. I've started using 'ref readonly' and stuff like that in bits and pieces of my application code, but the rest of it is basically written in a .NET 4.0 style and it's fine, there's no obligation to use the new stuff unless you want to. I've started using some of the newer syntax sugar to make things more concise, like local functions, value tuples, and short property definitions - but again that's totally optional.