I have travelled with my familiy PE for the last 4/5 trips and its very worth it for the resons given before, at Orlando they let you off quickly and you get your bagge and car hire quickly as well as the perks on Flight.
Last year we saw Jonathan Ross come off our flight at Gatwick and all of his bags were first up!
Travelling one better in August Upper both ways, i have been luck to have PE upgraded a few times to UC but this will be the frist time actually booking it in advance both ways.