No, liberation sans is not hinted. The only good hinted fonts that are available by default are the DejaVu series and the Bitstream series (essentially the same font).
I know about all the hinting settings, but that's not the problem here. The problem here is that the default Gnome Desktop is set to 'full' hinting. This in combination with Nimbus Sans getting used for all kinds of websites gives an ugly result.
I'm don't think that having metric-compatible results should be preferred over having fonts that look good under the default settings. The difference in quality is quite striking. Given that OO and other programs have historically had problems with fonts, I don't think people have high expectations.. but if you make every site that specifies Arial look like crap, then you're going to get a lot more complaints, since there are a lot of them.
Can metric equivalent aliasing be made optional?
The real problem is that there different fonts have different levels of hinting, and there's no good default setting that optimizes all the different fonts.