I went to OBA, and it is like everything else - it is what you make it. I, and all my house mates there had a great time. Others who didn't put the work in, didn't have enough time (you need 4 weeks minimum despite what they say), or arrived with a boatload of attitude, had a less good time.
PM me if you have any queries about OBA, or read slopeair.com - I blogged it onto there at the time (Nov 2005).