Joel,
Right now UML is not available on the Mac due to this Eclipse bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=67384
However, there’s really good news in that all of the pieces are available for this to be fixed. The only remaining issue is that Apple needs to ship their side of the fix in a Java update and they’re working on this now. Once it’s available, we’ll test internally and then enable the UML features on the Mac in the 5.0 timeframe, if all goes well.
The features that are non-Mac are tagged on the main news page under the product features here: http://myeclipseide.com/index.php.
For a difference of what’s in Pro vs Standard, please see this: http://www.myeclipseide.com/images/credit_card/me_pro_info.html
Oh, and if you want MyEclipse to run on an Intel Mac, you’ll need to wait for MyEclipse 5.0 Milestone 1 for Eclipse 3.2RCx that we plan to ship in a day or two. Details on that are here: http://myeclipseide.com/PNphpBB2+file-viewtopic-t-10163.html