I have the series and movie on a Zune and often let the series play while I'm working.
The marathons are great because I'll occasionally catch something that I've missed. One thing that I only noticed a few months ago was in the pilot, close to the beginning ... Nice little detail.
I have the reunion show (Firefly: Browncoats Unite) on the DVR.
Here's a nice little promo music video that SCI did for the marathon. If you're spoiler-averse, please don't watch ...