United has really improved their BOB offerings over the last year. Adding tasty salads and sandwiches, vegetarian options, enhanced snack boxes, and premium alcohol has made UA the leading domestic legacy carrier when it comes to onboard dining in Economy, with the possible exception of Continental, which still offers complimentary meals on many flights.
My new favorite UA BOB product is mySmoothie, offered on most flights over two hours. The Swedish smoothies are tasty and healthy--often a hard combination to find. I have tried a variety of flavors and recommend the raspberry smoothie if you have a choice. For $3, you can't go wrong.
Kudos to UA for offering healthy food and beverage options, particularly the highly-addictive smoothies!