I've been in the Microsoft programmer's camp since I've been consulting.  Java has a lot of great features, but when it comes to a business needing an affordable solution that can be built quickly, Microsoft has always been the leader for me. 

With the advent of Microsoft Visual Studio Express, I'm loving life!  Free Microsoft products, rapid design and development tools, and generous licensing terms.

Here are my (humble) opinions of some Microsoft .NET technologies:

• Streams - How can you avoid them?  File streams, network streams, fast and efficient.
• Databases and Data binding - How can you avoid this, either?
• XML - It took a little adjustment coming from MSXML, but worth it.
• Encryption - Easy to implement and understand.
• Visio Interop - I like embedding Visio into tools where conceptual diagrams can be extended to save design and programming time.
• Regular Expressions - A little investment in learning this goes a long, long way.  I've helped programmers replace 20 lines of code with 2 lines, using RegEx.
• Web Services - The Service Oriented Architecture is prevalent in VoiceXML programming.
• Reflection - Dynamically using assemblies at runtime - very good!
• Disassembling assemblies - What can I say?  I reverse Java classes and .NET assemblies; I'm a fan of erudition.  Yes, and a geek, too, I suppose!