Oh, hang on, I wasn't contesting that. Loaded with valid points. But the thing is, ZP as a medium has to focus on the negative side of games. Would you purchase BioShock based on his bit? It's a purposefully one-sided look at games; he takes an in-depth look at what's wrong and barely a glance at what isn't unless the game wowed his pants of (see: Portal).
My contention is that if you're going to purposefully highlight only one side, then you're technically being biased, since you'll never going to give the full picture.
Now Yahtzee simply doesn't know RPGs, and he knows even less about PC RPGs, so yes, if you shove the Witcher into his hands his negative valid points turn into negative invalid points. But they're still purposefully negative points, valid or not.
To me, there's a difference between focusing on the negative and not being consistent or knowledgable about that which he writes. I have no problem with the satirical and "negative tone" aspects of his reviews, and indeed that's probably the source of much of the humour. You can remain partially objective even if you have the intention to be negative, as long as you don't lose sight of what you're dealing with. It wouldn't be the best source of objective journalism, for sure, but it would still be useful to me as long as he remained informed and consistent.
I have a problem when he jumps around in his views, which is exactly how I read his complaints about the complex and "hardcore" nature of the Witcher. In several of his previous commentaries, he's bitched endlessly about the dumbing down of many games, like the case was with Halo 3 and Bioshock. He was craving more complex features, including RPG features like a traditional inventory (Bioshock) and lamented how it was obviously simplified for the console tards. Sure, you could make a case that he didn't want such features like they were implemented in the Witcher, but if you have an understanding of the genre you will know that the implementation is not a big negative in an objective sense.
Naturally, I can't prove that he has changed, but to me he's increasingly becoming more about the inventive bitching, than the excellent points he used to include - a gimmick as you say. The end result is a much less amusing and much less useful site, but this is all about my own personal opinion.
I should also note that I never buy products based on reviews, or at least extremely rarely. I just take pleasure in reading (or listening) to reviews that are made by informed and objective people. It helps me to articulate my own points of view and sometimes it even manages to change my mind about the occasional title. So, I would never use any review site as a guide to my purchases. It's just another way to pass the time.
If I had followed his review, I might not have bought Bioshock, no. Though I found he was reasonably fair regarding the good points, and I'm a huge fan of that particular subgenre, so I don't think his negative tone would have dissuaded me. In fact, that was one review where I agreed almost 100% and had I done it myself, I might very well have sounded equally negative and I don't have a need to be gimmicky. So, you see, I never considered the site a pure gimmick, and I'm still not convinced that was his original intention - at least not all the way.