This is incorrect. You can quantitatively measure "quality", and all it takes is a little effort to define criteria. The easiest example I can think of is measuring the average amount of time required for users to complete a task. For things like web sites, this can be gathered trivially via Analytics or any other stat program. There is nothing subjective about it -- if you do it right. Most usability professionals know how.

As for programmers working alone, though, that's something no one else can solve.

In general, sans serif fonts are more immediately legible, but serifed fonts are easier to read in larger blocks of text.

[citation needed] ;)

There's been a few studies that claimed this, but they had flawed methodologies. Unfortunately, it's lead to widespread misconceptions. Here's a relevant literature review with more information.

... someone finally makes an addon that wholly, completely, disables the StupidBar. Yes, I know about the about:config hacks and the existing addons. This is an issue I keep up with, after all.

And please, don't bother to reply if you're just going to parrot how much you LOVE the "Awesome Bar" and think I should give it an umpteenth chance. Been there, done that, still think it sucks.