People trying to book at the Hyatt (attached to the convention center, but not the party hotel) are reporting that reservations are going smoothly. Booking at the Crowne Plaza (my choice) and the Courtyard has been a bit rougher.
I picked the Crowne Plaza because (a) it's equidistant from the convention center and party hotels; (b) the room rate is better than the surrounding hotels; (c) I think the internet connection is included in the room rate instead of being an extra $9-$12/day the way it's likely to be in the other "upscale" hotels; and (c) I'm a Priority Club Gold member, partially due to having stayed in the Intercontinental at last year's Worldcon, but also because I like Holiday Inn Express hotels.
When I tried to book, it showed no rooms available. That seemed unlikely, and I reported it through channels. The D3 housing team were on it, and rooms showed up within an hour or so. Now as of that moment, only 1-king rooms were showing, not the 2-double I was trying to book, but it seemed prudent to go ahead and book the room at the con rate and worry about the room type later. I also left a message with the responsible person at the CP Denver itself. Not too long ago, I got a call back from that person, who explained that the only way to get any rooms on line today was to push the 1-kings out there; however, by giving her my booking number, she was able to manually change it to a 2-double. I expect we'll see all of the room types online soon, possibly as soon as tomorrow.
As I said elsewhere, I'm not surprised there were start-up glitches. I am impressed, however, at how quickly people have responded to try and fix things. Being trouble-free is an admirable but impossible goal; being able to fix problems when they happen, however, is excellent.