Not quite the first (Score 1)

I don't know that I would call this the first, though it may seem that way from the web-site. The Java Development Tools plug-in has been available for a while, as has the Jikes RVM plug-in.

Eclipse, for Java development, is definitely at a usable stage (both 1.0 and the 2.0 integration builds.) Very nice editing, refactoring, and VCS features (to name a few.)

I'm not sure why one would think that an open source development tools platform would constitute an attempt to block SUN. If you mean NetBeans, then, insofar as competition equals "blocking", I suppose you could say that.