"Uber" is perfectly pronounceable in German (I even gave a phonological example: /uːbɐ/). If umlauts weren't frequently stripped in English, there would be no reason to assume "uber" should be pronounced in any other way than how it is spelled, except hypercorrection (in other words: saying it wrong).

I'm not saying the word shouldn't be adapted at all, quite the opposite. I'm saying "correcting" the pronunciation to the one of the original German word it is historically based on is a bit silly because the English meaning of "uber" -- while the word itself may be derived from German "über" -- is actually quite specific and entirely different.

Now that I think about it, your "Müesli" example actually backfires. In (German) German, where "Müsli" has become a generic description for nearly any mix containing oats and milk (basically what you'll find on the German Wikipedia), the original Swiss word Müesli is often used with a much narrower and more specific meaning (equivalent with the original meaning of Birchermüesli, I think).

But anyway, for consistency I demand that you refer to Apple as Apfel (or Apful, if you want to stick with the original Old High German) and Microsoft as Mikrosanft (or -sacht? Etymology is a bit harder with this one) in spoken German, too.