For me, my favorite classes are the daytime classes on Wednesday and Friday.  There aren't a lot people there, and lately I have been the highest ranked student.  The perk of being the highest ranked student in class is that you get to be the training dummy for the instructor.

Why is this a perk? Because there is a big difference between "seeing" a black belt teach a technique and "feeling" a black belt teach a technique. I now have a much better understanding of what it means to pinch your knees together or drive your heels to the mat.  They sound simple enough, but there is a lot of room for interpretation.

Another perk is that you often feel something the instructor doesn't mention.  A lot of details are second nature to a black belt.  They forget to mention them because they don't realize they are doing it.  

If you can't be the training dummy, then I highly recomend private lessons.