Schools, in particular, I am concerned about. I know that home education is illegal there, for example, but not much about the schools/school system itself.
Plus, how easy is it to learn German? I know nothing except some vaguely remembered stuff from 2 years learning it at secondary school. 
Other things would be childcare, healthcare, cost of living, general attitudes towards children/family type stuff and anything else I may have forgotten.
This is all a bit hypothetical at the moment as DP has only applied for a job there, not got it yet, and even if he does me and DS might not end up going with him for a while (or at all) - if we do, then DS will be around 4 when we go. Provisional plan at the moment would possibly be to stay for a few years and by then hopefully DP is high up enough in the company to be able to request a transfer back to the UK. Of course this depends massively on circumstances. My feelings at the moment are that I'd love to spend a few years elsewhere but couldn't see myself living forever in another country.