No. No, I'm not. When I'm dining out, I'm almost never working, and if I am, what I'm working on is not the food, but rather the pile of papers next to my plate. If it's work for me to eat the food you've served me, you can be sure that even if I'm still hungry, I will let you take the plate. If, however, it's acceptably good, I am not working on it.
What I hate about this is that it turns the enjoyment of a meal into a mechanical process, and somehow it always feels like there's some implication of a duty on my part to keep slogging away until I'm good and done.
I've yet to come up with a satisfactory response to this question that indicates in a friendly way that the question is all wrong while also conveying the information the server wants.
Preferred approaches include: "Are you still enjoying your meal?" or "Have you finished enjoying your meal?" That's obviously the best, but also acceptable are: "Can I clear this for you or are you still dining?" or "Have you finished eating?"