Being a grad student at the University of Arizona on a fellowship has lots of variation. When everything is perfectly aligned (funding, projects, research, development, and classes) it is the most amazing experience possible. The faculty in the Electrical and Computer Engineering department are among the most intelligent people you'll ever meet. Generally you'll have a great deal of intellectual freedom. Each advisor is different, but mine let me direct my own research. This is good if you are self-motivated. One co-worker wasn't self-motivated and spent over 10 years with the same advisor, not graduating.
The work became very difficult when funding sources were drying up. I wanted to change directions for my PhD research from my Master's work. Writing proposals can take 40+ to 80+ hours, which you don't get paid for, aren't guaranteed to win, and sometimes the university is too slow to submit the paperwork (they have to review grant proposals) so you're never even in the competition for funding.
Great place with lots of smart people.
When your funding & research aren't aligned, you'll be putting in 80ish hours/week