Definitely worth it - one of the best moves you can make IMO. In fact, you might actually find you start liking the app a lot more - it's that much of an improvement over the version you're using. Yes, the UI is much better (the Reading Pane alone may be worth the investment) and there are new features that can really make Outlook a better place to live as well. My favorites are the Search Folders which give you a way to find related information across your Outlook store and gather them into a virtual folder.
There's a 60-day demo available. You might want to test drive it first (make sure you back up your .PST files first).