I am currently teaching Geometry, Algebra II, and Calculus (non-AP). Aside from my Calculus class, my classes are all fairly sizable, at 26, 28, and 30 students. Calculus, on the other hand, has only 10 students in it, so I get to know those students especially well. There were more signed up at the beginning of the year, but I think many of those students made the jump to AP Calc before the term began.
We are on trimesters, with 5 class periods a day (we call them "macros"). Each class period is 72 minutes long. We have a great building and a lot of resources available. I have a document camera and projector in my room. We do not have one-to-one technology, but there are laptop carts and computer labs available when I have a GeoGebra activity to do with my students.
One aspect of my teaching situation that has been a little bit challenging at times is the distribution of our math department throughout the building. There are two other math teachers in my wing of the building, but the other eight of them are spread out in other locations. When I am teaching the same class with those other teachers, I have to be deliberate about checking in with them and collaborating with them. There would be a lot more impromptu collaboration if the departments in our building were arranged by wing. I know others in Math 629 have mentioned much more real isolation, though, so this is only a minor challenge.
Another challenge, although I know it's not the least bit unique, has always been time. I feel this particularly in Geometry. Both halves of our Geometry course fit very tightly within a trimester.