Defo Scenery, organisation, and freindly competitors and marshalls make for a rewarding experience. I personally would tend to favour ultras with night sections and navigation - so The Bullock Smithy is probably my personal favourite - relaxed, very friendly event - covers varied scenery in the Peak District - a large proportion of it is at night...awesome event.
Another highly recommended event is 'The Classic quarter'
Ben there is always a high drop out rate - a mixture of inexperienced people taking on more they can chew or runners just underestimating the challenge of 56 miles (at minimum) over rough terrain partially at night... In terms of food at checkpoints I thought it was it a little thinner at some of them, although jam sandwiches are great, and the soup at Millers dale & hot-dog at Brand Top were great.