Pietro is a wonderful guy. I took two upper div classes with him and worked in his lab, and I can say that he is both an excellent teacher and a mentor. His class is very entertaining and he took one of the hardest subjects in physics (E&M) and actually made it doable. He spent the most time focusing on the useful aspects of the material and ignored the unimportant stuff. It was refreshing to have a young and energetic professor for what are typically thought of as the hardest upper div physics classes.
Working for him has been great as well. PBPL (Particle Beam Physics Lab) is a fun lab with a bunch of great people. To any physics students out there looking for a good research opportunity, there seems to be funding, and PBPL is a great place to work.

His course is not particularly difficult until the second half of the material, for Diffraction and Interference. He knows what he is talking about, but for these sections specifically, it is hard to grasp what he is saying and his pictures suck.

Otherwise, his midterms are straightforward, but again, by the second half of the course, it's hard to know what formulas are relevant.

Musumeci is a great in class lecturer. I could follow him much better than Corbin and he was funny and gave cool demos. His tests were also reasonable. The Mastering Physics is of course an overpriced piece of crap but the homework problems were still useful in preparing for his tests. His lecture notes are useful and pretty organized. He is the best physics professor I have had at UCLA. He honestly teaches better in big groups - I found him to be not that approachable during office hours.

Honestly, this was the hardest class I took in the physics department here at UCLA, and I didn't learn much--way harder than 110B, 112, 18L, and the rest. Musumeci is a convoluted lecturer (probably because he treats us as though we already know the material), and the exams are unfair (derive the shape of a spinning planet, Euler angles of a satellite, etc). Suggestion: avoid.

Great professor. He clearly cares about his student's learning and can be funny at times. His lectures are clear and he explains things very well. The homework often took a long time but I felt the questions asked were relevant to what would be on the midterm. The sole exception to this was Lagrangians for me since the homework questions felt leagues easier than what was asked on the midterm. His tests are HARD, though, and I had difficulties completing them within the time limit. The average for the first midterm was ~70% and the average for the second was 48%. There's also a Mathematica portion to this class but it's nothing too bad (only 6 homeworks in total). He also gave two Mathematica projects as extra credit.

Prof Musumeci is great. His love of soccer and his accelerator "downstairs" is so funny. Lectures are very enjoyable and he is willing to stop to answer questions. The HW are hard (even though they are straight from Marion and Thornton which has a solution manual) because sometimes I can't even understand the solutions. The exams are timed for an hour which is stressful with the online format because sometimes you get unforeseen tech issues. The questions definitely hard, but at least our atrocious average (40 something percent on the second MT I think?) got curved in the end.
Beware, this class does have a 2-hr mathematica lab section that is not shown on the schedule and mathematica hw was 10% of our grade (mathematica was also on the second MT). It's not too bad though because you don't really have to go to the labs to complete the assignments, since Corbin posts his notebooks after every lab.