I did my Erasmus at Istanbul Technical Universitesi (ITÜ) and I really enjoyed my experience there. The campus is one of the best campuses I have ever seen. It is literally like a small city where you can find anything you need (supermarket, restaurants, coffees…). Moreover, the international department of the university helps you to enrol in the different subjects. Besides they also provide you indications for obtaining your residence permit and arrange all legal staff if you are a foreigner.
In general, professors enjoy teaching and help you with any doubt you might have. In general, lessons are easy to follow and the exercises of the exams are similar to what you have seen in class. You will not have any problem passing any of them. The only thing that you should take into account is to check that your subject is taught in English because some of the subjects are in Turkish. Nevertheless, since on the same campus there are many different engineering faculties, there are some doubled subjects. Thus if you have overlapping lessons you can find the same subject on other faculties, this will ease your studies agreement. Another important point is that attendance is mandatory, you must attend at least 70% of the lessons of every subject. Of course, there are some exceptions where professors do not care about assistance and do not control it.
About the housing, I think that the best choice is to share an apartment around the neighbourhoods of Besiktas, Sisli, or Taksim. It is also desirable that when your rent the apartment you demand to your homely to include on the rent price the facilities such as water and electricity. All these facilities need to be arranged with the Turkish administration and no one will speak English there thus it will be very difficult for you to do it on your own. Another really good option is to share the flat with some Turkish people. I found my flat in a group on Facebook where people look for roommates. After some skype meetings, I decided to live with a Turkish girl that ease my life a lot there.
About the city, Istanbul is a wonderful place. There you will discover plenty of different cultures. Furthermore, Istanbul is a city where there is always something to visit. I didn’t have any problem while living there and to my surprise, I felt that the city was safer than many of the other European cities where I have lived. Besides it is very easy to travel around Turkey from Istanbul because you can easily and cheaply take a domestic flight to any point in the country. If I have to say any backward is that dimension of the city is that big that going every day to the university or almost anywhere takes at least 45 min by public transport. Hopefully, there are a lot of subway lines and busses. However, traffic jumps are very frequent, especially at the end of the afternoon.
Overall I think it is a great opportunity for you to discover new things so if you have the chance do not hesitate about it.