That’s essentially correct, Michael, though as explained in the post above, “It's pretty cheap for us to add support for additional browsers to OWA Light, since we don't have many advanced AJAX behaviors in it. But OWA2007 Premium is among the most advanced AJAX applications on the planet and there are literally hundreds of small browser specific tweaks and modifications we would need to figure out to make it work flawlessly in Firefox.”
This is not situation where we could have simply reallocated the OWA Light resources and make Premium work on Firefox and Safari. We needed to invest in OWA Light for *all* multi-browser/OS support, including older and unsupported browsers like IE on the Mac and older versions of Windows, which can’t support rich AJAX behaviors, to ensure that everybody had access to the rich features available in Exchange 2007; features like the Scheduling Assistant, Ambiguous Name Resolution, and Search. We also needed to invest in OWA Light to create the best possible experience for our blind and low-vision users, for whom much of the AJAX code in our Premium client would be rendered poorly, or not at all. As such, Firefox and other browser support was both critical for us, and relatively cheap for us, to include in the overall client matrix for OWA Light, but prohibitively expensive in the other features that we would need to cut to add it to OWA Premium for this release.
Personally speaking, my wife only uses a Mac, I’m an avid user of Firefox, and many of our team members our multi-platform users both in and out of the office. As such our team has a passion to make the best experience that we can for *all* of our users, with the resources and time available to us. :)