The one benefit to the marathon packages is that you lock in the 2009 room rate price for 2010. That means that any prices increases that go into effect when they announce the 2010 rack rates won't affect you. For example, we booked WL with the marathon package for $225 a night and it stayed that price, even though the 2009 rate when up to $240. Not a huge bonus, but it is something.
The other bonus is that you get the first crack at room availability before the "crowds". Yes, the general public can still book for 2010, but there's much fewer people doing it before the rates are officially announced. So, if you have your heart set on a certain resort with a certain room type or view, it's worth it to book with the marathon package. You're pretty much guaranteed to get what you want. Then, if room discounts are released for January (as they were with the buy 4/get 7 deal this year) you can call and try to apply the discount to your booking. You may get the deal, you may not, based on availability, but at the very least, you have something booked. We ended up getting a 40% off PIN for our stay at WL, and applied that to our "marathon package" reservation that we made made over 6 months earlier.
So, the short answer is no, the marathon package is not a good deal. It's just 2009 rack rate, but they're letting you book it earlier than everyone else because of the marathon, so that's at least worth something. If you have your heart set on a particular resort, I'd book now and watch for deals. However, if you aren't picky, I'd wait and see what comes out.
Just my $0.02, for what it's worth.
Edited to add: Oh, and we were only able to book room only when we called to book the marathon package. I had to call in August once the rates were announced to add passes and the dining plan. It looks like if you book online you can add passes, but not the dining plan yet. But it is no problem to call up and add the dining plan!