I've heard various stories over the years about evaluations for CVW -- are they done, do they count, how much do they count, etc.
Here's my take. The primary purpose of CVW is to provide well-qualified candidates an opportunity to learn more about USNA. I wouldn't be at all surprised if the mid who escorts you around is asked to provide some form of evaluation. However, as noted above, USNA realizes the person doing the evaluating is a plebe and this may be the first time he/she has evaluated anyone for anything.
Thus, absent your doing something incredibly stupid, the evaluation is unlikely to carry much weight. What is incredibly stupid? Here are a few examples:
-- saying the only reason you want to attend USNA is that your mother/father/sibling/teacher, etc. is forcing you to to do so
-- being totally negative about everything you see and do
-- being totally unable to keep up physically
-- making inappropriate comments (i.e., racist, bigoted, etc.)
-- making comments about how you hate the military, can't imagine serving, wouldn't ever want to go to war, etc.
And, quite frankly, if you fall into one of the above categories, USNA probably isn't for you.
Asking lots of questions, even "stupid" ones, is perfectly okay.

That's one of the purposes of CVW -- for you to be able to talk to plebes and see what their lives are like.