I can honestly say that I have enjoyed having all of my professors. Of course I have moments when all I am thinking is "did you really have to assign this? it is so pointless and so on", but in the end for the most part they only assign things that will be beneficial to you. Also, I must say that ratemyprofessor.com is amazing because you don't have to be anxious about what your professors will be like you can get reviews at your fingertips whenever you like. I think that was a tool for me because I was able to see the good and the bad before deciding whether or not I wanted to take the professor.
BU is a hard school and the professors are tough, but that doesn't mean they aren't very open to helping students and trying to help them be successful. They hold (usually multiple) office hours every week, are very communicative through e-mails and open to feedback. Professors WANT us to do well and to really learn the material.
The professors at BU are surprisingly accessible. They have numerous office hours and are always willing to meet with you outside of their specified hours. That being said, they're not going to force you to come to their office hours. It's up to you to make the effort.
My professors were collectively AWESOME. For the price you pay for university, they better be! My mentor teacher for my major is my inspiration, to this day. She is the reason I attended BU (story for another time), and a huge reason why I excel today, having graduated and moved on to newer things. She is friendly and warm, and eccentric. She always tied her hair in a bun with a pencil/pen in it, and used many 'unconventional' teaching methods to get her point across. I went to school in the College of Fine Arts, where you can be sure to meet a very wide variety of personalities. World-class orchestral players teaching part-time when they aren't playing in the Boston Symphony Orchestra, dramatic actors and other creative artists. My liberal arts teachers included professors who published modern translations of ancient Greek literature, world-famous archaeologists who actively travel to digs in obscure Egyptian ruins, passionate Shakespeare buffs, and so many more. I can say, with all complete honesty, that I never had a professor I did not like and truly respect. Perhaps I was just lucky, or am easily pleased. However, I do attribute BU's success in part to the world-class staff here at the school.