Project Tango (a.k.a. WSIT) enables Java interoperability with Microsoft's Windows Commmunication Foundation. Our
milestone 3 release features
a redesigned IDE that makes using security features much easier
more complete coverage of interop plugfest scenarios
performance improvements (our internal measurements show us to be on par with the other side of the wire, if you know what I mean)
interesting article on
Project Tango. Having participated in all the plugfest trips to Redmond, I can attest that the engineer-to-engineer relations between Sun and Microsoft engineers is very good --- we both like solving problems and building systems.