Sadly, Firefox 2 isn't dead (and apparently still accounts for 40% of Firefox usage), so inline-block is even further-away than the death of IE6. I recently had to take out a bundle of inline-blocks I had put in for a client's intranet site after finding out that they wouldn't even consider updating past 2.0.0.20. Why go through the major effort of transitioning to a new browser and then doing QA and testing for all your existing web-apps, but then not put in the small amount of effort involved in keeping said browser up-to-date? I've never seen a single site, no matter how complex, break on a Firefox upgrade.