The more important issue is, are you aware enough to judge the experience people are having around you as well as your own? I feel some critics are not, but Nagrant is.
I believe that Nagrant is more capable than most (I personally think that anonymity is imaginary and overrated) but it's hard to meaningfully assess another diner's meal without actually tasting it. Yes, you can gauge their physical response to it, you can observe (to a degree) how the food is cooked and plated, and you can even ask the other diners about it. And all this only applies to the tables that are visible from the critics' vantage point. But in the end, what one observes of others' experiences in restaurants -- even by a skilled critic -- is only worth so much.
For me, the more important issue is can a reviewer meaningfully and honestly assess food cooked by someone with whom the reviewer has a pre-existing personal or professional relationship? Will Mr. Nagrant end up reviewing restaurants helmed by folks he knows or has worked with in the past? If so, I'm guessing that these situations will be the biggest challenge for him, as they would be for any of us. I believe he'll be as deft in this area as one can be but it still it seems to be the most difficult aspect of being a credible critic, especially since our own biases are not always so easy to discern or own up to.
=R=
By protecting others, you save yourself. If you only think of yourself, you'll only destroy yourself. --Kambei Shimada
Every human interaction is an opportunity for disappointment --RS
There's a horse loose in a hospital --JM
That don't impress me much --Shania Twain