Worth it? I think so but it's a matter of how much you like the extra conveniences. The docx files are smaller and there are some bells and whistles that make it worth it for me.
I can't check the actual menu right now but I'm positive there's an Import Outlook Express mailboxes and contacts and I'm almost positive it will ask you if you want to import Outlook Express stuff upon installation. I much prefer Outlook to Outlook Express.