Small point about, why not have one mailbox and smart folder everything. This is fine if you have a modest amount of email, but not when it’s your main communication mechanism.

I only keep smart folders for tracking flagged messages and recent work email. I stopped making smart folders for MailTag projects because well… on my little G4 1.25 powerbook, blowing through my email for a particular MailTag project each time I click the smart folder is well — slow. I’m not sold on smart folders, but clearly sold on MailActOn and MailTags2. I do use spotlight but only when searching not for day to day folder browsing. I’m willing to take the performance hit of spotlighting my email to save eyeballing the particular email I’m looking for, but all the time when I click on mail folders — I’ll pass.