Ranked in these QuestionsQuestion Ranking
Pro Pleasant aesthetics
The font has a rounded, smooth aesthetic that is particularly appealing.
Pro Excellent readability
Line thickness, shape, and spacing help you to recognize characters and words correctly the first time through, without your eyes having to skip back and re-read.
Pro Easily distinguishable characters
There are dotted zeros in Ubuntu Mono so to distinguish from the letter "O", while the lowercase letter "l" is very different from the number "1".
Pro Many languages
1,200 glyphs, 200-250 languages (native languages of 3 billion people).
Pro Legible even at small sizes
The fonts retain legibility and under subpixel rendering at small sizes.
Pro Open source font
SIL Open Font License.
Con Many characters seem imbalanced
Some of the characters don't feel like they match well which can be distracting.
Con Lowercase "m" is weird and stands out
The lowercase "m" in Ubuntu Mono really stands out because of its unusual shape, which disrupts the user's attention when reading.
Con The font is too small
Ubuntu's 13pt looks like 10pt of another font.
Con No support for combined unicode characters
For example, x̄ is rendered as x ̄.
Con Dotted zero characters less distinguishable
Dotted zero characters are much less distinguishable than those that are slashed.