I've never used those but how can it be so much better than eclipse + all the commercial plugins? Closed source can never beat open source in the end...
I spend more time than I'd like in Eclipse these days, and am consistently underwhelmed. It just can't hang with the intellisense features of VS.NET.
I spend entirely too much time in Eclipse hitting ctrl+space and getting nothing back. Often even when the thing I'm looking for is in the same file, let alone included thru an import. ReSharper will find references for things I haven't even imported. It really is that much better.
Oh, and VS.NET does have open source and commercial plugins (of which ReSharper is a good example.) It's every bit as open as Eclipse as far as extensibility is concerned.
In general, I find it's best when offering comparisons of two products to have actually used both products. That is the basis by which I consider VS.NET to be superior to Eclipse. I'd suggest you try them both before making up your mind for good.
I don't see any compelling reason to switch off of Java for the VS stack... maybe if I end up needing to do consulting, I will learn these. I'd probably have to buy a windows license first :( One point I'd like to make is that eclipse is based on an open standard (OSGi) and having worked at a company that features an eclipse plugin, having the eclipse code open source is damn useful.
Spend a week writing C# in Visual Studio.NET with ReSharper installed, then try to go back to your old language and IDE. You'll understand.