University of Warsaw offers a variety of faculties and specializations so you can most probably find one that matches your interests. I studied there linguistics and I am satisfied with the practical courses. If you are motivated you can get the best out of this experience and improve your language skills. However, I believe the University should also develop your overall knowledge and attitudes, empower their students but I did not feel it is taking care of this area of personal development enough. It is definitely worth combining your Warsaw experience with an Erasmus one – you should not have troubles with the formalities.
The minus points of the University is its administration and lack of pro-student attitude I did not feel truly welcomed or inspired to develop my knowledge although it is considered to be one of the most prestigious ones to study at in Poland.
What I can recommend is combining your educational experience with the practical one by joining one of the student organizations. It was something that made my student time more enjoyable and interesting. The one I decided to get involved in is European Students’ Forum AEGEE-Warszawa where I met students from different Warsaw universities but also different corners of Europe and discovered new things about others and myself.