(Currently, IE returns the tagnames in uppercase, which is a separate issue — see https://connect.microsoft.com/IE/feedback/details/752283.)
The problem here is IE doesn’t escape " into &quot; at the moment, which is a potential security risk (XSS vector).
For this reason, Chrome escapes " into &quot;. Firefox is going to change its behavior to do the same: https://bugzilla.mozilla.org/show_bug.cgi?id=352437 Update: they just landed this change in Firefox/Spidermonkey (August 4th, 2012).
Opera will change its behavior too, if other browsers change (see bug DSK-369206).
Here’s a list of the methods that have this issue: