I think that java is good for .net in that the designers where able to look at java and make design decisions based on what is right and what is wrong with the java implementation.  On the other hand .net is good for java because many of the great features of .net will find their way into java via open sources projects and/or additions to the language.

One place where java is lacking is XML serialization of objects.  In .net this is very trivial and the whole thing can be controlled by attributes.  In java attributes are new to 1.5 and there is no built in serialization.  Fotuneately, java has a huge open-source community.  I've found a product named Xstream which makes object to xml serialization very easy.  A couple caveats: version 1.1 does not handle serializing properties to attributes.  Also, serialization must be controlled through code as java just got attributes so you can't mark a property with an attribute in the code to control serialization. 

I've used Xstream and it is very easy to use.  If you are looking for a very easy serialization library for java then Xstream is your best bet.  I have not found another library that works like this and is at a production level. 

Here is the link:  http://xstream.codehaus.org