David, crowds aren't usually a problem, neither is congestion apart from when the weather's extraordinarily good and there's a special line-up (Such as the FAA formation & Seafire debut last year).
I'd recommend getting there as early as possible for the simple reason that there's a great deal to see around the hangars before the show starts. There's also the flightline walk, which can get booked up, so it makes sense to get booked in on this and have a wander up and down the flightline for some unrivaled access to these wonderful machines.
Here are a few photos from the other week to serve as a taster for the season ahead:
http://forum.planetalk.net/viewtopic.php?t=3755
http://forum.planetalk.net/viewtopic.php?t=3749
http://forum.planetalk.net/viewtopic.php?t=3744
I hope you enjoy your visit,
Rob Leigh
(Fat bloke with big camera in hi-vis waistcoat)