I've always had this issue with Internet Explorer and hoped it would be resolved with the IE9 (RC) but it has not. Specifically, when I have a tab open with my Yahoo! Mail inbox, my computer consumes a steady minimum of at least 50% CPU when idle. Any further user interaction with Yahoo! mail causes my CPU to spike upwards to 100%, making navigation around my inbox extremely sluggish.
I do not have this issue with the Google Chrome browser which leaves my CPU idling around 0% when a tab is left open in my Yahoo! Mail inbox and navigation is easy when I interact with it.
This is just one example of a site where there is a very noticeable performance difference between Google Chrome and Internet Explorer. Performance issues have been the main reason I switched from IE to Chrome within the past year. I was hoping to see significant improvements in performance with the IE9 (RC), but this is not the case, especially with Yahoo! Mail.
I'm under the impression that Yahoo! Mail is script intensive and that I'm seeing the difference between the script engines of these two browsers, but this is only a guess on my part.
If anyone else has noticed this issue or can offer additional insights, I'd appreciate any feedback you can contribute, thanks.