I’m just trying out Eclipse 3.5-RC4. One of the big new features for me is that it’s now based on Cocoa instead of Carbon. There are many benefits to this, including being able to run on 64-bit Java 6. Fundamentally, it just looks and feels a little bit more mac-like.
As an example, one nice little mac feature I use a bit is “lookup this word in the dictionary”. If you hit Ctrl-Cmd-D
and hover over a word, you get an in-place definition. Eclipse now does this:

It doesn’t work everywhere (which you can probably guess from the context of that screenshot), but it is an indicator that Eclipse & mac are coming together. This is great news for Java developers on the mac.
Oh, it does feel a little bit faster too, which can’t hurt.