John Scalzi is back from Germany, and he says he's happy that I was not a vegetarian. In comments, someone agrees.
There's a pervasive myth that German food consists entirely of meat, notably in the form of sausage. I can assure you it doesn't. It's true that a lot of the traditional recipes are based on meat, and there are a lot of sausages, but there are a lot of other options. Yes, even in traditional restaurants.
I've been vegetarian since 1993. I spent my junior year of college (1996-97) living in Germany. I had, frankly, a much easier time eating vegetarian there than I did in my college's dining hall in Pennsylvania, or than I do eating here in North Carolina -- where even the vegetables have meat in them (often in the form of a hambone thrown in, or bits of bacon), at least in traditional Southern restaurants. Germans caught on to the organic food thing much earlier than Americans. I had probably the best soy sausage in my life while I was living in Marburg, picked up at a Bioladen (organic food shop) and grilled for Canada Day (one of my neighbors was Canadian).
When in Germany, if I'm staying in a pension (akin to a B&B), I eat the traditional breakfast: rolls, cheese, butter, jam, Nutella, quark, muesli, soft-boiled eggs. Everything except the cold cuts. If I'm in a hotel, I'll pop over to a bakery or cafe and get a pastry or two: nut-nougat croissant, pretzel roll, cheese roll. Left to my own devices (with a kitchen and grocery store), I eat the same thing I do here: cereal and milk.
For lunch, there's always falafel or vegetarian döner, pizza, sandwiches from the bakery (or your own kitchen), or whatever sounds interesting. For dinner, you can sit down anywhere. I've had really good Indian food in Munich, a nice Mission-style burrito in Berlin, vegetarian Maultaschen (also in Berlin), spinach strudel, baked pasta casserole, South Asian fusion (also in Berlin), amazing brown butter tortellini (in Berlin), delicious cheese spaetzle in Vienna...
I think you get the point by now, and I'm not the only one who's had a relatively easy time eating as a vegetarian in Germany. The folks at Happy Cow have a section for Germany to help you out, and I've found that Lonely Planet guides are good at pointing out places that have veg*n options as well as listing some straight-up veg*n places. (They're my favorite guide books, and they've never steered me wrong.)