Microsoft is trying to compensate his previous mistakes, I think .NET was a greate step toward this aim, In front of Sun's J2EE technology .NET has alot to say, the competition would never end!
From my point of view (which is very important!!) .NET would win the competition from performance point of view, unlike Java, .NET codes will be compiled twice, the second level compilation will produce smaller code,more efficient regarding the platform architecture and totally with higher performance, but(!) I'm not trusting Microsoft's products from reliability point of view,the future will show.
One of the very obvious points one can realise from these technologies is the extensive growth of XML, both Sun's "One" architecture based on J2EE and Microsoft's .NET have outlined their unified architucture based on XML. But where ever they are, Apache XML group is still ahead, This group will be one of the most successful open source groups very soon,wait and see.