A version of .NET is included in every Windows installation so you could say it is a part of the OS. If you have an ATI/AMD graphics card, you can’t update your drivers without having at least .NET 2.0. An ever increasing amount of other software is employing the framework as well. It has reached the point where you could say it is practically essential.

I have never had a problem with a .NET update since it first came out. My only complaint is that sometimes the updating takes a very long time to complete, especially on older machines.