I can certainly tell my clients to use Firefox for all administration - but it has it's own little flaws with the editor :)
I read the thread you point to and although I don't disagree, it is obviously impossible to change the worlds internet habits - at least at my level. My clients would be firing me tomorrow (and there would be 100 developers in line to take my place) if I told them I wasn't supporting IE anymore.
It's a necessary evil that always needs to be dealt with.