August 2007 was the first August date ever if I remember correctly. So, the data is rather tough. Being ready for either summer date is ideal. For regular admission schools, the PharmCAS applications don't even get sent out until late July to early August so there isn't a huge effect on your application relative to the October and January dates.
Like tharper14 said, the curve is based off of a standard from the 1998-2003 test takers. Even if your form and/or administration scored relatively lower due to difficulty, that is corrected.