Until I got my new laptop, I'd always used Outlook Express as my email client. There wasn't any particular reason for it other than habit. However, I'm now using Outlook for email because it has much better spam filtering (and lots of other goodies as I'm discovering).
One problem though: searching didn't work. Even if I searched for a keyword I knew was in a message, it always returned no results. Apparently, this is pretty common, given all the messages on various forums about this problem. There are a variety of possible causes, but mine was caused by installing an Office 2003 component (in this case, FrontPage, which is not available with Office 2007). Fortunately, the fix was easy: repair Office 2007 as described here and then rebuild the index (not mentioned in that article but necessary nonetheless: choose Indexing Options from the Control Panel, then click Advanced and click Rebuild). Now my searches are lightning-fast, which is about a bazillion times faster than Outlook Express was.
As an aside, I purchased a copy of Microsoft Expression Web, the replacement for FrontPage, and promptly uninstalled Frontpage. So far, I like Expression Web. I'm not much of a Web page designer; I just need to maintain a couple of sites without too much fancy stuff. My favorite feature in Expression Web is master pages, which allows you to create a template for your Web site and then just add the content to each specific page.