Apparently, some Radiohead fans are incensed that that pay-what-you-want download is 160 kbps MP3s: this is a very low compression rate for most music fans who believe that it doesn't sound as good, especially on a stereo.
I've listened to the album and the fans are both right and wrong. They're right that it doesn't sound as good: it's got a bit of a hollow sound and would be more noticeable on a stereo. They're wrong in being upset though; Radiohead is presumably not stupid enough to give out their album for free and giving people a chance to hear the whole thing for free before it sells in stores is a fair deal. Besides, most listeners aren't going to notice the difference when they listen to this album on their IPod, and one assumes that the average radio-fed listener will be perfectly happy with the free version. And, a few of us old farts might still argue that, if sound quality is your overwhelming concern, you'd be better off not buying any digital media in the first place.
All that aside, Radiohead probably could have made the compression rate clear before downloading began.