This version for Mac OS X is much improved over the previous version. It looks more Mac-like, though is still an obvious port of a windows xp program.

Some nit-picks:
While the floating palettes are a welcome (and overdue) update, they are not true to Mac interface guidelines in that their position is restricted to being inside the build window. As a result, if the palettes are at the edge of a large build window and you make the window smaller, the palettes stay within the frame of the window and get "covered-up" rather than floating above the window.

The implementation of the brick palette also feels awkward and inconvenient. A tabbed or browser design alá Apple's iApps would have been better.

Overall, this version of LDD is a better application than it predecessor, but is still not a true Mac OS X application. Nevertheless, recommended.