I like Open Sans because it is easy to read on relatively low resolution screens. It is a lot like Droid Sans in that respect.
In fact both Droid Sans and Open Sans were created by the same person. Open Sans has more weights and styles than Droid Sans however.
easily installed by the way if you want it..
then go to downloads.. right click , extract here, then open the open sans folder and double click on each .ttf, click install , password when prompted, choose if just personal access or system and run install. repeat for others as needed.
as with all extras, do check that you are legal to use this font in your country before you install and do note that any extras you install outside of the default wattos package, you do so at your own risk.
Or, from the link in my post above, click "Open Open Sans in Google Fonts"
Then click the download arrow on the right side of the page.
My suggestion is to add this font to wattos.
Open Sans iseems to be included in Debian package "texlive-fonts-extra".
But I do not recommend this package installation because the package has many collecting fonts.