Would love to see Report Builder available for the Mac. Out of my last 3 jobs, I've only been able to use it once for this reason. Not willing to get a PC just for Report Builder, but it would be huge to begin using this tool once again.
We are looking into this fairly seriously. As you may know, with historical versions of Excel for Mac a plug-in like Report Builder would not have been possible. Newer versions, based on Office365, do allow for robust plug-ins. Your organization would need to be on Office365 to use the plug-in.
I would love to make use of this, after moving over to mac I'm having to keep hold of a pc solely for Report Builder, there must be a tonne of marketers and UXers in the same situation.
I also have a Mac. I keep Parallels with Windows 7 and Excel on it for the sole purpose of being able to use ReportBuilder. Love love love this "Omniture Idea"