Yes, we started registration for those that pre-registered on Wednesday night/Thursday morning. For those that did not pre-register, we'll be opening registration for everyone else in a week or so. And to answer Matt's question, yes, it's on.
We've been committed from the beginning.
As to the airport to fly in to, yes, O'Hare is closer and more convenient for HostingCon 2005. There is a free airport shuttle to the hotel from O'Hare. However, as moosh28 said, Midway is also an option. You'll probably need to take a taxi to/from the hotel, which I would *estimate* would run you about $20-$30, so figure that cost into your flight costs to see if you'll really save money.
Let me know if you have any other questions. I'd be happy to try to answer any that you may have.