Hi
No, it is not at all difficult to pass the semesters in IIT once you get through JEE. after working hard so much for jee, passing the semester will be a cakewalk for anyone. bt yes you will still have to study a bit.
All u need to remember after coming to IITs is that u r still a student and u have to study to pass. IIT courses are designed in such a way that u need to study well to get a good grade. Although there are some courses which are too difficult and a bit of an extra effort. That's whr some students find difficulties and yield, but tilll u r sincere and regular, u wont face any difficulty.