According to the latest Amazon Japan DVD sales rankings, both the Haruhi and K-On! DVD releases are performing quite well. Of particular interest are the K-On Blu-ray releases, with the Volume 2 Blu-ray (August 19 release) occupying the #2 ranking, Volume 1 at #16, and the Volume 3 (September 16 release) at #21.
The first Endless Eight Haruhi DVD (September 25 release) is currently ranked at #11, but has accrued quite a few negative one-star reviews, for a cumulative score of 1.5 stars. This would seem to indicate that Japanese fans are just as frustrated with Endless Eight as we are, but are still willing to purchase the DVDs.