Tom!!!
First thought when I saw the title of your thread 'AH! there he is, something funny!! it's been a while'
After hearing enough 'Oh, you look great!', 'you look MUCH better than the last time I saw you' (this is an easy one for the other subject: they don't need to ask if treatment is going well, they decide themselves it is working great), 'still, you're not at all looking sick', blablabla... I'm just standing there 'Oh, thank you sooo MUCH' - lol - I think it's better than expressing what I really think about what they are saying...
Saying someone looks great is such an easy and lazy comment...