I hear Neo and Dvorak are popular among Germans (both score better in German vs English typing). I personally didn't like Dvorak for English, some of the letters were too awkward when it came to rolling and low same-hand-rate feels unproductive, but many people prefer that (the way I see it, Dvorak is good for the slow "hunt-n-peckers", the layout in German may be better though). If you type a lot in English then Colemak is great. It's also pretty good for Vim, since the HJKL cluster is placed conveniently out of the way, but within reach and in logical order (google for reference). It's also one of the easiest to switch to from QWERTY, and since so many letters are in the original place, it will be much better for default shortcuts. Some people swear by Workman (mod from Colemak), but I don't see the appeal. It promotes a poor typing technique and shoots itself in the leg by increasing same finger usage among many other things. But it has some loyal fans, so it can't be all that bad. None the less, almost anything is better than QWERTY.
When it comes to special characters, I recommend you place them as you feel is best for what ever language you use and ignore the original authors design. Try something and keep changing the layout until you are happy with it. You can also use a function button to place your most used characters on the homerow for example.
Keep in mind that once you switch layouts, you'll decrease your productivity significantly for at least a month or two, so do it during a holiday. Switching to a keyboard like ErgoDox and placing symbols on the homerow is already a much greater improvement than switching layouts will be, so think twice before dong so. It will also make it awkward to use someone else's computer after a while. But if you're serious about using the computer a lot then a more ergonomic layout is a good thing to do.
