I don't actually mind the commitment; in "only need post something if you want" situations, I tend to second-guess myself and end up not posting anything. Having a commitment, a deadline, and a penalty gives me a chance of actually finishing something. (Having prompts also helps. If "no commitment necessary" isn't my writing nemesis, it's "write anything you like".)

The most difficult part of Yuletide for me is thinking of something to ask for. I got over that hump last year because, for once, I really wanted fic about a particular thing, and once I had one request I managed to come up with a few more by thinking about my favourite obscure fandoms and looking at what other people had nominated. But I don't want anything in particular this time out, and I'm not feeling any enthusiasm for recycling the leftover requests from last year.