We stayed in the Luxor, and first night we couldn't be bothered to go far - this was our main motive for trying this place out. As an "all you can eat" / self-serve sort of place, it is very much as you would expect in that you queue up, pay at check-in, and go when you've finished.
I'd have to say that the quality and choice, compared to other (sometimes cheaper) options on the Strip, was not great. You did not, for example, get the rib/shrimp that the Excalibur offered, and the choice of beverages was not as wide as the Excalibur's either. The "Italian" options were the ropiest. The pizza was dull and dry and the pasta sticky and soggy.
I can say that, bar the pickiest of eaters, you will find something tasty to fill up on. There are meat and fish dishes (mostly in sauces and gravys to keep them moist, obviously) and salad, fresh fruit, a couple of soups, and a dessert counter. The desserts were things like apple pie and cheesecake - they were OK.
I'd say that at about $19 a head, you can do better without much searching. OK if you're in the Luxor and can't be bothered to walk - not worth the walk if you're not.