Nevertheless I'm working mostly with Java right now, Microsoft .NET platform and C# is also the stuff I'm very interested to know. I've been developing on Microsoft .NET since 2002 and I'm really excited how such efforts and investments Microsoft is putting to it. Sun seems to miss the train ...
Java 1.5 had been a great, innovative release either of the language and platform. Sun's answer to Microsoft's C# 2.0. But not enough ... Microsoft delivered C# 3.0 so far with great features inside: enhanced initialization (type instances & collections), anonymous types and delegates, LINQ, lambda-functions ( == closures) ... As a developer, I'm really excited about those things. Many of them I would like to have in Java as well.
1) Collection initialization
This is a most wanted featured I guess. Any modern language has to support it. Groovy is very good complementary of Java with excellent language syntax tradeoffs.
3) Class initialization by property names
4) Enhanced generics (parametrized types) support
Even Java 1.5 brings something like C# generics (which both are similar to C++ templates), the Java's implementation is the worst. It's my point of view.
5) Default type value
Hope, Sun is going to thieve something from C# in put it to the Java. Will see ...