As a web-developer you don't have to worry about IE5.5 now, in 2008, seven years after the release of IE 6.0. Seven years to make sure your site works in IE 6.0. Seven years time to upgrade to IE 6.0.
If Microsoft goes through with what they've promised, one day you've got a web site which works on the latest version of IE, and the next day (when MS releases IE 8) you don't.
Since all web pages aren't going to be fixed in a day, practically nobody will upgrade.
The only solution is to do what they did for version 7, and 6, and 5.5. Maybe they could have prevented the problem by releasing a more standard-compliant IE 5, but since then, they're stuck.
The good thing is that we're slowly getting better at abstracting the problem away.
If Microsoft goes through with what they've promised, one day you've got a web site which works on the latest version of IE, and the next day (when MS releases IE 8) you don't.
Since all web pages aren't going to be fixed in a day, practically nobody will upgrade.
The only solution is to do what they did for version 7, and 6, and 5.5. Maybe they could have prevented the problem by releasing a more standard-compliant IE 5, but since then, they're stuck.
The good thing is that we're slowly getting better at abstracting the problem away.