I love the simplicity. I love that jamming the mouse into the upper-right is the way to bring up all the application launching and window management UI, and the rest of the time it's out of the way. I love that it actually feels innovative, in that the design isn't just ripped off from some other OS. I love that non-essential features are relegated to extensions, keeping the core pure.
IIRC the problem with Eclipse is that it still uses gtk2, and thus gtk3 themes and config won't affect it. You have to manually edit the gtk2 settings to apply a reasonable theme. Ironically KDE can control gtk2 from its own control panel, but GNOME 3 cannot. Oh well.
Personally, I don't understand how any serious developer can use Mac OSX, yet almost every developer I meet these days in fact uses it, so... perhaps we are just projecting.