Before you ask, it appears the online version will support Firefox and Safari, as well as the ubiquitous Internet Explorer.
Is Microsoft nuts? Maybe not. The software giant is fighting free versions that do pretty much everything Office does. Microsoft apparently believes it can hook people on the free version, while getting them in the tent and anxious to upgrade to the application version that will work better and faster and have some more features.
On the Mac side, Apple sells the iWork package for US$79.00 which is cheaper than any Mac version of Office available. There is also Neo Office (free-donation requested) and Think Free Office ($49.95) along with Google Docs -- which is not as feature rich as Office but it is offered at no cost. Open Office (free) is also a possibility. There is a version for both Intel Macs and PowerPC hardware.