> The most legible font is the one you're used to.
Maybe for you, but don't assume that is true for everybody. It took many months of trying various font rendering configurations (Infinality in ClearType-ish and OSX-ish modes as well as custom modes) before I settled on my current[1] configuration. I'm very familiar with having to spend some time adjusting to different modes, but in my opinion, this the differences in rendering greatly overshadowed the differences from seeing an unusual/new setup.
Perception of text on a screen is affected - at a minimum - by the rendering technique (AA, subpixel-AA, hinting, contrast of the font, contrast of the display, eyesight of the viewer, and the ambient lighting in the room. Maybe in your situation the subtleties of font rendering are not that important. On my monitor, I find [1] to be a lot easier to read than any of the examples (both before and after) that were linked in the announcement.
> very little value
I'm sure most people are fine with sensible defaults, but please, try to remember that "value" is often subjective. People even disagree about which criteria represent high value.
[1] http://i.imgur.com/wMWmNKt.png?1 (esp. the 12px row)
(No, you don't want to see my messy custom fontconfig configuration that overrides a LOT of fo0nts choices and forces them into the handful of fonts that I find easier to read. Yes, that took another few months of experimentation.)
edit:
> vector fonts were a mistake
That depends a lot on what you are doing with them. While I was talking about vector fonts, the amazing font
-xos4-terminus-medium-r-normal--14-140-72-72-c-80-iso10646-1
is still my favorite. Fortunately, it's easy to use both old-style bitmap fonts and modern fontconfig/freetype rendering in X. Each type of font can be used where they are appropriate. Honorable mention: "Dina".
If you doubt the benefit of a high-quality rendering of a (appropriately hinted) vector font, try loading [2] and [3] (source: a very enlightening article[4]) in separate tabs and switching between them (so the images are in the same position). Image [2] uses modern techniques to render each line 0.1px further right, accumulating 3px over 30 lines. The other image [3] rounds the x offset to the pixel grid. Modern rasterizing techniques can align font rendering to 1/256th of a pixel!
[2] http://www.antigrain.com/research/font_rasterization/sample_...
[3] http://www.antigrain.com/research/font_rasterization/sample_...
[4] http://www.antigrain.com/research/font_rasterization/index.h...