It was also a question for me: write in English or German? English would actually be preferred since more people can read it. On the other hand, I usually comment on German articles here - an English blog would be somehow a stylistic break. My old websites were mostly written in English (I won't link them here, whoever wants to can go on a treasure hunt for them). Newer ones mostly in German.
It's kind of funny - I keep hopping back and forth between the two languages. I can never really decide - the choice for new projects is usually rather arbitrary. But the Hugo stays in German. I still have the Timmy for English.
At owrede_log : interfacedesign.org there's the original article.