I think it's fair to ignore the expert opinion of both Oracle and Google employees on this matter.
It's, however, disturbing when Mueller pretends to be a neutral part, because, quite simply, he's not. The fact he's occasionally right doesn't make him honest. Or trustworthy.
Just out of curiosity, how is that different than, say, Rob Weir's (IBM employee) opinion taken pretty much as fact by everyone on the ODF/OOXML conflict, or for that matter why do we accept Pamela Jones' analysis and opinions if she is so clearly biased against Microsoft?
Facts are facts and opinions are opinions. I don't see a reason to confuse them at all.
However, Mueller's opinion has been considered to diverge from reality in very specific ways, always favoring whoever is paying for it at the time and always being presented as an unbiased expert opinion.
Having an opinion doesn't itself discount an opinion. Being biased or unreliable is reason to discount an opinion. It's important to remember that those are separate concepts.
Bias has nothing to do with how strongly you believe something to be true, or how hard you try to spread that opinion. Bias is nothing more than the extent to which your opinion differs from reality. If you consistently and vehemently insist that the earth is round and not flat, you aren't biased, you're right.
And regardless of bias, you have to also take into account the specific evidence and reasoning provided with an assertion. PJ in particular is pretty good about explaining her predictions, so you can't dismiss her solely due to her bias - you also have to find fault with her reasoning.
It's, however, disturbing when Mueller pretends to be a neutral part, because, quite simply, he's not. The fact he's occasionally right doesn't make him honest. Or trustworthy.