Unfortunately, the Liberation fonts aren't well hinted, with antialiasing off. This means that for those of us who value sharp contrast and clarity more than beauty and fidelity-of-typeface, they don't work well.
There are three ways to make fonts work well on a pixel-based display.
[0. Fixed, non-scalabled fonts (the old 75dpi and 100dpi fonts).]
1. Antialias. This adds grey (and sometimes coloured) sub-pixels to avoid jagged outlines. It makes the letters well-shaped, and true to the typeface. C.f. "Cleartype". About 20% of people (including myself) find the effect most unpleasant: it sacrifices contrast, and makes the display look out-of-focus, causing eye-strain. All truetype fonts can be antialiased.
2. Hinting. The shape of the letters is distorted (at small size) so that the lines fit more naturally over the pixel-grid. The letters are sharp and clear. An "e" is no longer a "times new roman 'e'"; more "an optimised e-grid, that is slightly times-new-roman-ish". All pixels are either black or white. With full-hinting and no antialiasing, this works. BUT, you must use the libfreetype which has the "Bytecode interpreter" turned on, and one of the small subset of fonts that are well hinted, Tahoma being a good example.
3. Retina display. Make the pixel density so high that the issue disappears. (alternatively, make the fonts really large, eg 25pt, with antialiasing).
[My personal recommendation is 8pt Tahoma for the GUI, and Terminus for the shell; full hinting, no-antialiasing]