I don't think IE usage is still in the 90% range. Stats in my previous post on this topic, IE Market Share... and Why It Matters, show it in the low 80's and dropping - the July numbers show this trend is continuing. Remember that "alternative" browsers often report themselves as IE so they don't get "downlevel" HTML.
I think the decision that IE isn't a profit center outside of Windows releases was probably short sighted. Many things in software and technology are important for credibility (think Java for Sun, IBM nano research, etc.), and credibility is very important when it comes to technology purchases. For example, a small design (primarily Mac users) which has to deal with IE quirks all the time is unlikely to want to set up a W2K3 / Exchange mail system when they need e-mail, or go to IIS6 when they need a web server, etc. Don't just write that market segment off as a lost cause, because it wasn't a few years ago.
I probably wouldn't recommend that Microsoft get into the browser market right now if they weren't, but since they got in several years ago they don't have this luxury. Like it or not, Internet Explorer is part of Microsoft's brand identity. Business managers often approve technology purchases based on how they feel about a company, and bad feelings about IE for the non Windows XP crowd (including Windows 2000, for example) will cost sales of Microsoft products.
I don't see this changing either - see the July 6 IE chat transcript from aebrahim's blog. There's a lot of "we understand what you're asking for, we appreciate your feedback, we are evaluating this (but don't expect anything besides XP SP2 and Longhorn)". That's how I've been taught to politely tell someone no in the business software world. I empathize with the IE team, I just don't think they have the high level support they need to compete here.
Having enough of problems with IE, I'm switching to Mozilla Firefox today.
...To summarize: IE guys, you have to get out of year 1999 as soon as possible. When people say Microsoft, they think Windows and IE. This is the most common. Losing IE for Mozilla or Opera you are giving away a lot more than some small percent of users - you're giving away a lot of brand recognition. How can anybody forget about the first and most used application of his clients? Is this arrogant or just overlooking? How can you say you want to provide the very best experience to users when the most important tool, an icon of our times, browser which is the very first computing experience of many people, is so broken?
So, make me come back to IE. Or maybe nobody cares?