hi, former UVa grad student. a few thoughts:
The AFC (undergrad gym) is hella nice, i never used northgrounds gym, but i heard it is not as good (well that is if you are lifting). the AFC tends to get crowded during peak times, so i would suggest going really early or really late (or around 3 pm).
Club clemons is really true, well kind of. for grad/professional students you wont ever run into people you know, because generally only undergrads study there. i occasionally would run into students, but not often, so if you need a place to study where no one will find you i think it could be an option.
Alderman is a total nightmare, i never studied there, because it was impossible to find a good space, unless you actually have a study carroll (which i think usually go to PhD folks who are done with coursework). there is a place called the scholars lab in alderman http://www.lib.virginia.edu/scholarslab/
which is super hot, has huge computer screens (great for working on large projects where you need to be able to have a few pdfs and a word doc open and viewable all at the same time. there are also little areas that have two or three computers near each other that work well for group projects. This spot fills up early, so if you want to use the space you need to arrive early.
i havent read all 10000 pages of this thread, so i dont know what the food talk was, but seriously do yourself a favor: during your first week please go to the downtown ped mall and visit Marco & Lucas. they serve asian noodles and dumplings and they are delicious and cheap.
let me know if you have any questions as i am happy to oblige with whatever info i have.