I'm not a fan of dubbing. Sadly, if you're from a country that has a big enough population to afford good quality dubbing, they usually don't leave you a choice. So as soon as I could (like, for my level of English) I switched to English pretty much. It's not as much the voices that bother me than how they translate it.
Like when Spike says "I may be love's bitch, but at least I'm man enough to admit it"...you would never use bitch in German in such a context. So what they did is they changed it to 'I might be a victim of my feelings...", which doesn't have the same ring. Buffy had a lot of witty dialogue, but when they try to translate it into German it just sounds douchey.
I do sometimes watch stuff dubbed in French though, for educational purposes. I kinda like that, because a year ago I bascially didn't understand anything (though I did already know basic French...took it 4 years in high school) and now I could understand all the French dialogues up there.