You stated, " we don't user DNN core Content localization in production."
I assume there is a good reason for that decision. Is it because you have had bad experiences in using the core localization code?  Would you mind elaborating?

I am asking because I plan to change the default/reference language of my website to German and then to use the (core) DNN localization process to create the corresponding pages in English. Of course I will have a DNN backup before I begin. Nevertheless, if you can offer me any tips & tricks regarding this task then I would be grateful.  

Can I assume therefore that you have developed your own solution to the localization problem. If this assumption is correct then does your DNN consulting business sell the software and knowhow necessary enable the creation of an efficient, SEO-friendly, user-friendly and bug-free multi-lingual DNN website? 

With each release of DNN, especially in the current generation (i.e. v7), I see a lot of effort and investment directed at the localization problem and I am confident that eventually an industrial-grade solution will exist. However in the meantime, I am reluctant to use the core DNN localization feature; I'm worried that an upgrade will cause major problems to a working website. In your opinion, are these concerns of mine justified? 

Daniel