Is Visual Studio 2010 RC ready for production? [closed]-Collection of common programming errors
I wouldn’t start building a mission critical application using .NET 4.0 just yet. I’d use it to see some of the new features and get comfortable with it [as microsoft always love to move things around].
This is an entirely new runtime they’ve built, so it’s a much bigger chance than 2.0 to 3.5.
So, basically, don’t bet your career on it just yet but definitely use it.