The installation instructions required clarification as to the required eclipse version - 3.2 is the minimum version required, but newer versions will work.
Downloading the Tersus components as a zip file is not required (unless you are planning an offline installation - see the sections Online Installation Procedure vs. Offline Installation Procedure
While skipping Installing SMTP Mail Support will not render the studio nonfunctional, some plugins (obviously Send Email, but also Show File and possibly others) will not work.
With regards to your org.eclipse.gef_3.0.1 error, are you making a clean install, or are you installing over an existing eclipse/studio installation? Either way it would help to get more info (logs, list of installed features/plugins, etc.) - Note that you can use the Insert/edit image button below to include a screenshot if you wish, press the ... (browse) button to select the file to upload.
Creating mac (and linux) specific installation kits would be great, but I don't think that will happen any time soon. A community-based initiative might change that.
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