The Web Quick Search is excellent for Address Book entries.
But it is almost useless for Opportunities and Customer Service Cases as it doesn't allow you to search by Company or Contact Name.
Jin Yu commented
Searching opportunities by Address Book entry is already in product. When you search opportunities using Quick Search, you can select Address Book Entry parameter from the drop-down, or type in ab: in the search field. The Quick Search will search for opportunities based on the Address Book entry. The same function is also available for searching cases.
Joe Glosik commented
We must be able to search opportunities by Company name.