Very impressed by the whole organisation - very slick compared to other events I've done, great goody bag, good car parking and marshalling, iconic track etc.
Can't comment on the lack of atmosphere - felt fine to me...
My Garmin also 'over-read' the distance at 13.34 miles. So that's about 400 yards over. I'll believe the guy who said the course was properly measured, but I also believe my Garmin, so not being able to apex each corner seems to have added 400 yards (or about 2 minutes at my speed).
Overall though, it's an event I aspire to do again next year - many thanks Adidas, Silverstone, and all the marshalls!