Speaking as the one of the majority of flyers (not necessarily the majority of FTers) who rarely get the privilege of flying in premium cabins, I think many of the negative comments are unfounded.
I fly in international premium cabins once every few years, when I've saved up enough miles to take a really nice trip with my wife - usually to celebrate an anniversary. For the vast majority of flyers who are accustomed to flying coach, international J is incredibly luxurious.
As far as food - I've always been perfectly satisfied. If United hired only the best chefs and cooked to order on the plane, there would still be plenty of people on this board that would complain about how horrible the food is.
I don't drink, so my only complaint there is that they don't carry any diet soft drinks other than Coke.
There is no way I can sleep in a coach seat, but the lie-flat seats are very comfortable, and being able to stretch out and sleep while flying is a luxury only dreamed about when I was younger.
The only other airlines I've flown in J are LH and AA. In my limited experience, the UA product has been better than my experiences on either of those airlines. I'm sure there are some better products, but unless you are the kind of person who finds fault with everything, you'll like it.