This has to be the weakest excuse ever for dogding the question when we all know the answer : OWA on non IE browser is crippled for 1 main reason: Microsoft doesn't want you using non IE browsers. Get with it guys and realize that no one company controls the web and forcing limitations on non IE browser is about as 1995 as you can get. The largest software company in the world can't development, test and support the second most (and climbing) popular browser in the world? Please. I smell dirty politics and then some. Dump the 'Light' experience and put those people on making it work THE SAME across ALL modern browsers.
Joseph: Firefox users will get the "OWA2007 Light" experience, which is a much improved rewrite of "OWA2003 Basic". Listen in on the posts to the Exchange blog and you should see a post on "OWA Light" before long.