Mail synching didn't work at all in the PM versions I've tried. They may have fixed it, but really it's not needed.
Your service provider will most likely provide a BIS (blackberry internet service) with your blackberry plan. This will allow you to add multiple POP3 or IMAP email accounts.
Check with your email hosts for your personal and business accounts and see if they support IMAP as IMAP accounts on your blackberry will give you the added benefit of copying your sent messages to your mail server.
Set your email client on your mac (Mail or Entourage or whatever) to delete the mail off the server 1 day or more after checking (or not delete at all, depending on your storage limits on your email account). This will make sure your blackberry still gets email when your email client is open.
That's it. Leave the syncing to contacts and calendar.