I take photos discretely and with an aim not to disrupt others around me. If I plan to take a lot of photos, I usually ask for a seat not too close to other diners if possible.
A lot of people ask me what I had at a particular restaurant and it's far easier to send a few photos. Also, since I've started to write restaurant reviews for Executive Road Warrior, the photos are not only good for the articles but also better than my attempts at note-taking during a meal.