Mac OS X's Mail app has been my preferred email tool since I started using the operating system back in the Public Beta days. I never got into Microsoft's Entourage, despite being an Outlook Express user up until that point. Mail has nicely evolved as my own email usage has grown, first with the addition of solid message filtering and later with the Junk mail filter, which I find I trust more than The Register's ISP-maintained server-end solution.
Mac OS X 10.4 takes Mail to version 2.0, and the improvements are mainly cosmetic. Mail 2.0's modified user interface has come in for some criticism, but I like it. If the new icons are too large when you first run the app, or you don't like the multi-part buttons, you can easily customise the toolbar to suit your personal preference. Similarly, you can customise the toolbars of new and incoming messages opened in a window of their own. You can also select which fields you want a New Message window to show, which is handy if you're not interested in all the cc: and bcc: stuff, or you want to make the new mail priority selector appear.
Moving the Mailbox list from an Aqua drawer into a full frame within the mail readout window not only looks better but makes more sense - the drawer metaphor implies the contents are not something you want exposed all the time, but that's exactly what you want if you have multiple mailbox folders into which you filter emails.
Had I been starting out with Mail 2.0 from scratch, I might have ignored the filter feature and gone instead for Smart Mailboxes, Mail's version of iTunes' Smart Playlists and Finder's Smart Folders. Unlike the Finder version, Mail's Smart Mailboxes allow both AND and OR logic, and you can sort on all the usual attributes. For me, they provide a more ad hoc way of collating certain emails - think of them as a kind of saved Spotlight search. Indeed, searches made using the customary search field can be saved and they appear as Smart Mailboxes.
Speaking of Spotlight, Mail's searching is now based on Spotlight, so it's immediate and narrows down as you type more characters. Crucially, you can now search across all mailboxes rather than just the one you happen to be viewing.
Another tweak borrowed from elsewhere in Mac OS X are slideshows for emailed graphics, which makes viewing photos from family and friends a real pleasure. If you have iPhoto installed, you can have Mail send any or all of the pictures to your library. Apple has fixed the glitch where email attachments copied by drag and drop rather than the Save button would retain the read/write permissions of the sender rather than the recipient.
Sending pictures is easier too, thanks to a new ability to auto-resize shots either to minimise the attachment size, to ensure recipients can see all of the picture straight away, or both. Signatures can now be applied on a per-account basis, which is handy if, like me, you use Mail to manage both personal and professional emails.
For the more technically inclined Mail 2.0 provides a handy window - right-click or Control-click on the mailbox's name in the right-hand panel - to see what's on your mail server before you download the files and allow you to delete them immediately. There's a quota manager in there too, but you'll need an IMAP mail account to make use of it. Apple has added a Connection Doctor, which checks your server connections, so you can see whether a downed server or a ropey Internet connection is preventing your mail from getting through.
There are still irritations: manually empty either the Deleted or Junk mailboxes, and it still asks you if you want to. If we can be trusted to empty the Trash without being asked, I'm sure we're sufficiently responsible to be allowed to do so with rubbish emails. And why does the Erase Junk Mail warning appear as a regular dialog box while the Erase Deleted Messages warning is an Aqua sheet? Right, let's rehearse the Apple UI mantra: consistency, consistency, consistency...