Rated 5 out of 5 stars
Best addition ever. With Expression Search you can drop the buildt-in gloda and quickfilter because this add-on it combines both in one location. Additionally it extends the search features so you'll find exactly what you search.
No idea why this is also called GMailUI but whatever.
For those who also have to work with Outlook and miss the old Lookout Search: this is the similar approach on TB, only better.