I've been watching the discussion with increasing interest.
The language tag is very important but very simple and looks like this
<META NAME="language" content="en">
or like this for a .de site
<META NAME="language" content="de">
I run over 400 sites in Germany and can only advise you to stay away from any combination of English and German.
Several attempts to earn some money with exit-free US erotic-stuff failed completely and that is quite frankly amazing.
You don't need to give good money out for google.de!
Try one of the many local free submitters.
Make sure that all Titles, Descriptions and Keywords are relevant and have enough drawing-power of their own.
Let an online-submitter spider your site and you're on your way!
You get a free submission to perhaps 120+ of the better SEs and Catalogues and if the keywords are half-way good, google.de, Lycos and Co. will find you within 2 - 3 weeks.
An excellent helper is always dmoz.org but don't forget: everything in German!
I have never paid a cent for ratings and enough of my sites get first-page SE-Results to keep me happy.
What more does one need?
A .de domain is an absolute Must!
Swiss and austrian surfers come over here in droves ....!
Is it important to protect a trademark or similar?
Then register a .com and a .net with the same name as the .de domain! Otherwise you could have a problem, because here everyone copies everyone else, if the topic is at all attractive.
You would be amazed, when you knew how many variations there are to the word "Partnerprogramm", there must be 20 Sites out there, all in German!
In Germany we are not fussy about the TLD so long as the site is in German!