Although I don't know if I will be doing the XNA one either -- I think that just spending a couple of hours to hack away at something new is excellent experience. I was not too enthusiastic about the JQuery challenge but I found that hacking away a the DIC interface was fun. I learned a little about how DIC's rss feeds work, I got a chance to practice a little at Ajax, not to mention working with some JQuery events... It was fun.
Besides I suppose you could look at it this way: i bet you are excited to see some people try their hands at some functional programming -- you could at least be polite enough to tolerate brief excursions outside of your comfort zones.
SO I do hope that you will participate in SOME that are a little sideways for you.
Well, of course I will! I'm looking forward to challenges in languages I've done little in, and with stuff like Twitter that I've not messed with (Though, I've been playing with Twitter with Haskell lately. Even wrote a small function to update my status, and I'm working on figuring out OAuth now.). I never meant anything by what I said. A lot of people here really like XNA, so this will be fun for them. I was just expressing my own dismay. :>
As for the JQuery challenge, that just isn't my thing. I doubt I'll do many web-development related challenges.