It was worth the hassle... for Smart Mailboxes
Finally my dream has come true. Smart Mailboxes in Mail.app. Several times I nearly migrated to Entourage just to have this feature, but now thankfully I don't have to. I just created two smart mailboxes... "Today" and "Yesterday". And I just about cried when I saw the "Include items from Sent" checkbox in the New Smart Mailbox dialog box.
For years I've wanted this because I'm subscribed to so many lists, and they're all filtered to different mailboxes automatically, and it's a big pain to switch between them constantly to keep up to date. The mail client I used for years in the 90s in OS/2 and later Windows NT had the ability to set up filters as being "manual only", ie: they didn't fire when mail was received, only when you manually told the application to filter the selected messages. Back then I just made the mailing list filters manual. I'd leave the incoming list messages in my inbox and then every once in a while I'd select all in Inbox and hit the key combo to apply filters... and presto, my list mail was filed where it belonged.
PMMail still beats Mail.app in one thing... you could specify filter rules using a mini-programming-language. Essentially this let you write arbitrarily nested complex boolean expressions instead of the "any/all" approach Mail uses. Plus they had many more rule actions... for example you could add/remove people from groups, and to redirect messages to groups, meaning you could actually implement a fully functional mailing list system with subscribe/unsubscribe functionality using just a few filter rules. You could probably do this in Mail now using an AppleScript attached to a rule, but it's much harder to set up.
Re: disk space... I uninstalled iDVD (since I can't use it anyway) and converted more of the WAV files from my iTalk to Apple Lossless and now I've got over 3GB free.