I did the 1/2 day, and sucked. I did much worse on it than I did percentage-wise on the practice MBE and any of the released question sets in the MPQ2 book.
I wouldn't panic - I think it's the usual Bar/Bri strategy. They don't want people to slack, they want you to study harder, and they know we're all hitting the MPQ2 book late in the game, so they put a concentration of hard questions in these sets. It will make the real thing seem easier (I think), and make us all praise Bar/Bri's praises after the fact.