DVD reading and streaming seem like they'll take up most of the time, so I'm a little scared I won't have time to actually work on the player interface(though I probably won't be able to resist meddling with it...)
That's not necessarily a problem as long as you know it and mention it in your proposal. Last year I participated into GSoC as a student and I'm still working on things that were on my original proposal, one year later. I'm even paid to work on it this summer as part of the Haiku Code Drive. Starting a big project makes you more likely to continue contributing to Haiku after GSoC is over, and that's something we like.
-- Adrien Destugues / PulkoMandy http://pulkomandy.ath.cx