What open content Unicode fonts can be recommended?

We now have quite a good variety of free software Unicode fonts available, as can be seen from the Wikipedia free Unicode fonts overview. With that comes the difficulty to choose. So, here is my analysis in the context of searching a complete set of great free fonts for writing a thesis document:

My recommended fonts

• DejaVu Sans. Its web home is dejavu-fonts.org. Recommended to be used as the main font for the document (except you insist on a seirf font). Because, this font has great Unicode coverage and free software licencing, and as a unique feature among comparable fonts like FreeSans, it comes with  a “Light” variant. What is really missing for now is a “Light Condended” variant, however.
• Liberation Sans Narrow. Even more condensed than Liberation Sans, which is already more condensed than DejaVu Sans but comparable to DejaVu Sans Condensed. So it can be used as a “really condensed” font in replacement of a missing “DejaVu Sans Light Condended”, increasing the possibilities of document formatting. The downside is, this font lacks good Unicode coverage, so it can only be used for normal Latin text, not formulae etc..
• FreeSerif. A good-looking, free software licenced serif font with huge Unicode coverage.

My not-so-recommended fonts

In alphanumeric order.

•  CM-Super Sans. Like Modern Sans, this is also a PostScript Type1 conversion from the TeX Computer Modern font. And therefore, it is really good-looking. However, if any of these TeX fonts would be used, Latin Modern Sans would be preferrable.
  Because its Ubuntu package lmodern says in the description: “Their size is reasonable and they are usually considered to be of good quality (compared to cm-super, for instance; however, cm-super contains font families that have no equivalent in this package; additionally, there are character sets that are supported by cm-super and not by the Latin Modern fonts).” In addition, Wikipedia confirms this: “Other PostScript-based replacements exist such as BaKoMa, CM-super, or Latin Modern, instead of the original METAFONT-based Computer Modern. The Latin Modern implementation, maintained by Bogusław Jackowski and Janusz M. Nowacki, is now standard in the TeX community and was made through a METAFONT/MetaPost derivative called METATYPE1.” [source]. An advantage over the Latin Modern fonts is however that they contain fonts for all font sizes [source].
  Corresponding Ubuntu packages: cm-super, cm-super-x11. But for some reason, this does not make the sans serif font available to X11, or maybe not even install it.
• DejaVu Serif. For my taste, this font has a very bad look for a serif font.
• FreeSans. Comparable in good look to DejaVu Sans; FreeSans is just a bit more condensed. Comparable Unicode coverage as DejaVu Sans. However, this font lacks a “Light” variant.
• Latin Modern Sans. This is a PostScript Type1 conversion of the LaTeX Computer Modern font. As it’s coming from TeX, it’s definitely the best-looking free software licenced sans serif font [text examples]. However, it is not recommended here because it lacks sufficient Unicode coverage.
• Corresponding font names in LibreOffice: LMSans, LMSansDemiCond, LMSansQuot.
• Corresponding Ubuntu package: lmodern.
• Liberation Sans. This font is a bit more condensed than DejaVu Sans. Compared to DejaVu Sans, it misses the great Unicode coverage and also a “Light” typeface, which is the reason it was not recommended here. It has larger relative x-height than DejaVu Sans, which is said to make it less useful for large portions of text [source].
• Liberation Serif. Good-looking, screen readable serif font. Already using another font from this family is one reason more to use this serif font instead of adding a font from a third family. However, this font lacks big enough Unicode coverage, and cannot be used for that reason.
• Linux Libertine G. It is a way better looking serif font than DejaVu Serif, includes considerable Unicode support, but is less readable than Liberation Serif in small font sizes.
• Lucida Sans. This is not recommended here because it is not available under free licences; it is just included gratis with Java. What’s interesting however is the Lucida Math font for formulae.
• Nimbus Sans. Not recommedned to be used as teh default font because of lacking Unicode support and lack of a “Light” font weight in the free software licenced variant [source].

Technical note: If you are on Linux, do not check Unicode coverage of fonts with gucharmap, as it will simply take over non-available symbols from fonts that have them. Use the LibreOffice “special character” table instead.