I really liked studying at the University of Heidelberg. The Atmosphere, the people, the staff, organisation and campus.
Sometimes it was really annoying to choose courses because it says 'choose what you want' and on the other hand the courses fall at the same time which makes it really hard to do so.
I have done my exchange Semester in Lisbon at the ISEG and FLUL. ISEG had a good quality of studying, small classes and teachers who are willing to talk with the students about questions etc. At FLUL, the conditions were a bit worse but still had an okay studying life. All in all I loved my exchange in Lisbon with alle the life beyond university life of course as well.
The organization could be better, but the secretary and most of the teachers are very kind and helpful. There are many options of courses to choose. Overall in some ways the University of Heidelberg ist more expensive than others. You have to pay a lot for language classes and sports for example.