This is why http://thebookpatch.com just launched: To specifically address the writing needs of (book) authors with tools and features dedicated to, for example, character development. (IE users only. Not my product, though I did some contract work for them.)
Depends where you go. I have a (fairly) general interest site that gets about 100,000 unique visitors per month, and only about 55% of them use IE. Cutting out 45% of your potential market is quite a cost for a bit of lazy programming.
