Last night I was able to unknowingly attend what turned out to be the secret test screening of Half-Blood Prince in Chicago, IL. My review, which contains mild spoilers and plot details, can be found right here.
Important things of note are that the movie was amazing, and that the purpose of the test screenings is for the filmmakers to gain feedback in time to possibly make some changes to the film based on an audience's concerns. In other words, the film is in great hands and the finished product will be even better.
UPDATE: For those of you who were interested in a little bit more from me. My girlfriend and I recently sat down with my friends at Hogwarts Radio and were interviewed, for their podcast, with an hour-long Question-and-Answer session! More is discussed on their seventh episode than in my review here, so take a look! You can listen from their site or subscribe to their podcast on iTunes. The Q&As are very insightful and it was a pleasure to be able to talk about the film in that medium. Please note that there are a bit more spoilers – discussion was partly in response to other write-ups done on the film and in response to some of the comments already on this newspost. Thanks!