does anyone know anything about this uni...I've read info on the net but has anyone studied there and if so what was your experience

I haven't actually studied there myself but I know a couple people who did and they were full of praise. I know someone who is doing an economics PhD at the Humboldt Univrsity, and he is really happy there. Good research atmosphere, nice staff and very capable and friendly professors. Of course, this could be different in other departments, but the university has a good reputation in Germany.
Also, Berlin is awesome and much cheaper than other European cities of its size.

i agree - haven't studied there myself either, but know people who have. it is a well-known, high standard university.
as many german universities they have constant financial problems so are economising wherever they can. this may result in departments being dissolved and in bad teacher-to-student-ratios, and they don't have the means to invest into renovating buildings and such. if you can live with that, you'll be fine in berlin!

Agree with both Marbeaux and shani,

good university with excellent reputation