The academics here are decent. There's a lot to address, so I'll start out by talking about class difficulty.
Maybe the easiest way to explain class difficulties would be to categorize classes as either "easy" or "hard" (this is obviously a generalization, in reality, the difficulty of classes would be more accurately described as a spectrum, rather than two groupings). Easy classes you can get by by going to class and paying attention, and doing (maybe) a few hours of work per week outside of class (depending on the class, some mixture of reading, practice problems, projects and/or essays). Examples of "easy" classes that I've took include Intro to Macroeconomics, Intro to Sociology, Social Psychology, Logic, Modern Philosophy, and Brain and Behavior. "Hard" classes are different. They require you to go to class and pay close attention and take notes. They might require an average of an hour or two a day of work. It can be easy to fall behind in these classes if you are confused during lecture and can't find the time to catch up. This can be bad. Because the material is usually cumulative, if you fall behind, it has a snowball effect, because if you didn't understand last weeks lecture material, you'll have no clue what is going on in this weeks lecture. Also, what makes "hard" classes hard is often the tests. Sometimes (ex. Introductory Biology I and II) you'll put a good amount of time in, and know the material pretty well, but not do well on the test because of tricky/unfair questions. For example, in many science classes, class averages for tests will often/usually be in the 60s, and sometimes 50s. Assuming that the majority of the class isn't very stupid/lazy, this probably indicates either a hard test, or bad teaching. With that said, getting an A is never out of the question if you work hard (and smart). It's kinda hard to compare these "hard" classes with AP classes because AP classes seemed slower and more spread out, and also because high school is just different than college. However, I think these hard classes are a little/moderately harder than AP classes. Examples of "hard" classes that I've taken include Honors Calculus, Biology I and II, and Organic Chemistry I. I've also heard that physics classes tend to be hard.
Regarding the quality of professors, some where decent, some were disappointing. I haven't had that inspiring professor yet, although once in a while I hear of those cases. Again, it may be easiest to explain professors' quality as "good" or "bad". "Good" professors explain things in a logically consistent, and moderately clear way, and they'll also be pretty organized and fair. (A "truly good" professor, I think, not only explains things in a logically consistent way and is decently organized and fair, but they should make the material as clear as it can be, make it interesting and stimulate your thinking, and also provide the students with study material and practice questions that make it very easy for the student to study. I haven't had any "truly good" professors yet, although I've had some reglar "good" ones). "Bad" professors are very frustrating to encounter. They might not explain things in a logically consistent way, they might be confusing, have a bad accent, be very boring and not thought provoking, be disorganized and expect kids to know things that they shouldn't be expected to know, they might be lazy and not provide much to the students to study, and not prepare much for their lectures. I'm probably forgetting some characteristics of bad professors, but you know one when you see one, it's common sense. I obviously haven't had anyone who has all these (bad) characteristics, but I've definitely had professors with enough of them where I'd loosely categorize them as "bad". Hopefully, if you do get a bad professor, it'd be in an easy elective. If not, it'll be difficult to pull of a good grade, and you might not be as knowledgeable and interested in a core class for your major. At Pitt, there's a pretty normal ratio of "good":"bad" professors. It's important not to think of the quality I've been describing in absolute terms, but rather in relative (to other colleges) terms. I think that Pitt is pretty average academically.
Regarding scheduling, often times it can be frustrating and difficult to get into the classes you want (let alone getting the time slot that you want). Sometimes you may not even get into a class that is required for your major (ex. organic chemistry labs, biology labs). Another issue is that some (important) classes are only offered in fall, and others are only offered in spring. Still, the scheduling inconveniences are probably comparable to other schools (maybe a little worse than other schools).
Regarding the class "styles", it definitely depends on the class. I've been in a lot of natural and social science lectures. These have all been lectures with little if any class participation (although sometimes kids ask questions). Even during the recitations there isn't much participation. (Even in discussion oriented recitations, like Modern Philosophy and Intro to Sociology, kids aren't very eager to participate. Usually you'll get 2-4 students who are the "talkers" amongst a group of 20 students) However, it may be the case that I simply haven't encountered a class with much participation. I suspect that in some of the arts/humanities classes, as well as upper level classes in any field, the kids in the class are there because they like that field, rather than because it's a prerequisite, and thus are more inclined to discuss things.
Regarding the academic requirements, although they're pretty standard as far as colleges go, I still think they're a bit much. I have to take like 2 arts/humanities classes, 3 international related classes, and a literature class (in addition to the requirements I've already fulfilled), which seems a bit much considering I'm a neuroscience major. I think I could get enough exposure to these fields in 2-3 classes rather than 6.
Regarding the work ethic of students, it's hard to say because there are so many different types of kids. Most kids go to class (usually), try to pay attention (mostly), do some reading and homework throughout the week, and cram a good amount before the test. There are other kids that don't take work very seriously and don't do much work outside of class, and will also often miss class. Then there are kids who take work pretty seriously. These kids almost always go to class and pay attention, and they'll do a good amount of work throughout the week.
Two last messages. To people for whom Pitt may be a reach school, I think that with hard (and smart) work, you'll absolutely be fine. I don't think the difficulty level will be too high, as long as you put in a good amount of time and effort, and be efficient as well. To people who may have Pitt as a safety school, a few things to consider. Don't worry about it being too easy. You can definitely challenge yourself by taking a heavy/difficult course load, and you could gain valuable experience by volunteering, doing research, or participating in a club. On that note, because Pitt is such a big research university, there are a lot of opportunities to do research (one of Pitts strengths). You can also take graduate level courses (or courses next door at carnegie mellon). I know plenty of kids who could have went to an Ivy league school, but chose Pitt, and are definitely being sufficiently challenged. Also, lots of kids from Pitt win international scholarships, and go on to competitive graduate/professional schools. I think that shows that Pitt has a lot of resources that can allow you to achieve anything.