I have a suggestion for future Hair Fairs and although it probably won't go over very well, it is just a thought and my two cents.
Instead of having it in one location with the WORST lag I have ever experienced in my SL life, why not just advertise which vendors are participating and then just have them set it up in their own shop. They can advertise in their own store which ones are for the Hair Fair with their 50% signs like the ones they have up in the Hair Fair.
When you advertise the vendors on the blogs, advertise the hairstyles at the same time.
I'm sure that would not be as exciting but I am not even sure if I am going to try and go back to purchase any of the hair that I bought demos for because of the lag. I just don't have the RL time anymore to spend a lot of time trying to move just a few steps in SL to buy hair.
Again, just my two cents!