HORRID. If you can get out, get out! He is the worst professor I've ever had. You literally just have to memorize proofs. The entire class has no idea what he's talking about half the time, and he is a very poor communicator. Only take if you enjoy hearing "uh" or "um" every ten seconds. Seriously. First day of class I counted. I hit 100 "uh" or "um"s in 12 minutes. Biggest problem is that he assumes the students can see what he sees. He'll do complex math in his head and not show that step. very few people seemed to be able to follow his work very well. My TA was very frustrated with the questions he gave for midterms. Just run. Run.
I took the history of mathematics with Professor Mess. The class was not too difficult, but that was no thanks to him. He walks into class most likely wearing the shirt he wore the day before, writes stuff on the board and assumes that we understand it. Thankfully the material is not too difficult, and everything on the test comes directly from the book. The first midterm was pretty easy, although I have no idea how I did on it because he never returned the grades to us. What's curious is that the day after our second midterm, the grades were already online. So based on that test, I'm doing alright in the class, but I honestly have no idea. We were only assigned 4 homeworks, none of which we have gotten back. (Gene Kim is an amazing TA, he goes over most of the homework in section. TAKE HIM). In short, don't take Professor Mess. He strictly follows his last name. To. The. Smallest. Detail. His office looks like a small bomb went off, scattering papers everywhere. He often stands in front of the class thinking for minutes, just staring at us until he can formulate his thoughts. The one good thing is that 30% of the class is getting an A- or better, and 70% is getting a B- or better. At least there's an awesome curve.
Mess can be a little awkward, but overall cares a lot about his students. I took him for 123 and 106. His teaching and lectures are hard to follow but he stresses proofs above all else, especially the ones he does in class. He is an extremely easy grader. If you get the proof right, or almost right, or if you're on the right track you'll get full credit, or mostly full credit on the midterm and final.
Really disappointed, he makes me spend most of the time to study MYSELF!!!!!!!!!!! Workload is extremely heavy and takes me lots of time for finishing it. Paper is marked by his feeling and the grade can be quite out of expectation(usually much worse than expected). It is the course I have taken and got the poorest result, even though I spent most of the time for studying it!