My experiences doing a startup in Germany were generally positive. I never had an issue with language and found most of my German hires spoke English at least as well as a lot of my American hires did. Work ethic is strong. Technical skills are strong. Moving people and product around the EU is relatively easy.
In my experience, the culture of risk taking is fairly conservative. The good news is that when people commit to something, they almost always deliver it. The bad news is that it's often challenging to get people to attempt things that are not known to be achievable. There is definitely a different attitude about "failure" in Germany than in the US.
Taxes are somewhat high, but not unreasonably so and they rarely has much impact on startups. Employment taxes are sort of a swap relative to the US. On the one hand, they are higher in German. On the other hand, many things (like health insurance) are included in the German taxes where they are not in the US, but are still a required cost.
Employment laws are definitely challenging. It is hard and expensive to get rid of people. However, there are many ways around that and you should plan accordingly. It is important to have a good advisor/lawyer in Germany.
Access to investment is a mixed bag. It depends on your track record and your business. Definitely much harder than in the US. Having said that, especially in Berlin, it is decidedly available if you meet the criteria.