Really doesn't. My pet peeve is that there are 2 search bars. Search and Quick Search. The main search doesn't really work well when you want to say, search for emails sent by co-worker X.

You type in their name/email and you get this separate tab (so many tabs). There are things like To Me, From Me, Attachment, People, Starred and a bunch of statistics at the top. You can see a screen shot here: http://www.dagorret.net/wp-content/uploads/2010/01/thunderbi...

The regular search could be good for advanced searches. There are probably a bunch of options for it somewhere. But for most searches you really want the Quick Search which is some menu bar option.

Not sure what kind of design decision this is either. In Mail.app except for saved searches, I usually try a simp search, if that fails, then there is an option to try and refine it.