Done it one year, "proper" dressage horses seem to find it quite exciting being on grass in a big park! But there is loads and loads of room for warm-up etc, and it is much quieter than the show proper the following day. The arenas are flat.
i went last year i think, the only problem being that that flies/midges were horrific at that time so make sure u go armed with lots of fly spray! altho with the summer we're having they prob wont appear in the rain this year! good luck!
i went last year, the marking was VERY erratic - i got a stupidly high mark for a not very good test. My second test was really good and i got a very low mark with some odd comments - everyone was in the same boat tho.
Agree with the midges thing - flys were horrific.Also the arenas weren't cut so the grass was long and it was really bumpy and lots of horses kept stumbling.