I went to qualifying last year, I had a great day out. I thought Maggots and Becketts were the best as you're closer to the track.
Watch out for the over zealous security, who were kicking out anyone who dared to go near the under cover stand at Becketts, even though there was nobody in there!!
Also, it may only have been last year, but be careful when they direct you to a parking space, when I went someone made a huge cock up and loads of bikes were blocked in, making it almost impossible to get out when you wanted.
I thought the food wasn't too bad, bit pricey, but I've been ripped off worse than that, cheaper and probably nicer to take your own.
One more thing, my friend paid an arm and a leg for tickets into the paddock, supposedly to see the riders. All he saw where the trucks and closed garage doors, you get the impression the riders are a bit 'up themselves' and are far too fabulous to mix with any low life.