I've used this but it was also back in 2009. Lovely hotel, nice room and getting to the airport wasn't an issue but had to wait a while to be collected when we returned (around 20 mins), but no big deal overall
We used it in on our feb trip this year. It was great and good value. You give them your car keys in a special envelope when you check out and they take your car and park it.
When we came back, they picked us up from the terminal in 10 mins and our car was ready and waiting back at the hilton for us. A thumbs up from me.
I haven't done the park and fly thing but we stayed there last year before flying out. We got a deluxe room with breakfast for £60 which was really good. The breakfast was full english so sets you up for the day. The only thing id recommend is taking you tea with you for that night as the food was very expensive! The shuttle to the airport was really good and ran every 20 minutes.
We will definitely be booking it again this year.