SharePoint 2010 uses modal dialog boxes (very Web 2.0) to minimise sever requests. This speeds up the user experience over previous versions.
Many companies run IE because lets face it, it is a lot easier to deploy and lock down. However IE has never been the fastest browser. However with the 4th release of the preview of IE9 things may start to change. Realistically I don’t think IE will ever be the fastest browser on the market but I think it will be so close the majority of users will not notice a difference from the likes of Firefox, Opera and Chrome.
So if you are in IT and your company use SharePoint 2010 be prepared to roll out IE9 early 2011. But don’t wait try it out now in your development and test environments.