As a power user I need to use advanced search operators like 'site:' or 'filetype:' very often. With the new address bar this results in an error message:
Windows cannot find 'IE9 site:microsoft.com'. Check the spelling and try again.
Example of operators are listed here:
I can workaround this issue by (double) clicking onto on of the search providers listed at the bottom of the address bar drop down, but this is not acceptable for productive use! At least I would expect a shortcut to always forward my input to the currently active search engine (i.e. Shift+Enter).