I used Eclipse and Visual Studio extensievly too.

#1, both Eclipse and VS are open for plug in. Eclipse provides more tools but they are caused by Java itself. Any netural tool you can easily find counter part in VS as well.

#2, partially true if you need a complete Open Source solution. But in your own development, when you need a code snippet to save your investigation effort. I found .NET community provides more consistent and effective answers than Java.

#4, supporting .NET, more components companies such like Infragistics, Telerik etc. You need pay them, but you can be more concentrated on your business applications.