i LOVE westfield.
I don't have much money and only tend to shop in dorothy perkins/topshop/zara/warehouse/river etc, but i love having a whole day walking around westfield. It's nice as a change, I like looking around the shops i wouldn't normally go to, theres a lot of shops i had never even heard of before. I also love all the little stores in the middle of the mall, like a nice smoothie bar and ice cream store. I did chuckle when going through the 'posh' part (the Village?) where theres a champagne bar on show for all the rich ones who like to show everyone just how well off they are, sipping champers at 11am.
I agree that the eating part of the day is a bit shambolic. Been to westfield twice and both times went to pizza express. got there at 11.55am last time so was in pretty much straight away, last time queued for about half hour. They play fast music to make you eat fast and rush you out of your seats as soon as your plate is looking almost-finished.