The better of two options might be a 2 PM to 5:30 PM session – see if your company will pay you to attend, and keep Friday evening to yourself, regardless. But for everyone who’s going to be stuck at a desk or otherwise occupied, there’s also a 6 PM to 10 PM meeting. Or, as Ben Lisbakken writes on the Google Code Blog, "You are welcome to stay for both."
This sounds like a good opportunity to collect business cards and email addresses. And, if only because my lunchtime is just a few minutes away, we mustn’t forget about the aforementioned prizes and food.
RSVPs are required, but should be quick and easy to make.