Hi Ryan,
A formal policy doesn't exist. In general, we strive to support Internet Explorer and Firefox on the Windows platform, and Firefox and Safari on the Macintosh platform. Occasionally, there is a browser bug that causes us to remove our support for a particular version of a browser. This is the case with Firefox 3, although we are working with Mozilla to get Firefox 3 supported.
In general, Workspace should work with any browser that has a supporting Adobe Flash 9+ player. Our difficulties, such as the FF3 problem, come into play due to the fact that we use browser JavaScript to control an iFrame which is positioned over top of the workspace flash movie and contains the acrobat plugin.
I will discuss the idea of a formal support matrix with our documentation team, because I do think its a great idea. In the meantime, I am happy to answer any particular questions.
Matt MacKenzie
Engineering Manager, LiveCycle Process Management ES