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Pro Can display a lot of text due to narrow width
Consolas is really narrow compared to most monospace fonts. The more narrow each symbol, the more text you see on the line.
Pro Includes a large number of unicode ranges
Consolas supports 30+ unicode ranges including Greek, Cyrillic, and Thai for a total of 2735 glyphs.
Pro Nice appearance
Consolas has a good appearance and character without being too distracting.
Pro Available for Windows and OS X
The font is available on machines running Windows Vista, Windows 7, Windows 8, and Windows 8.1, as well as part of Microsoft Office 2007 and Microsoft Visual Studio 2010. Otherwise it can be downloaded from Microsoft's homepage. It can also be set up on OS X machines with instructions on how to do it available here.
Pro Differentiation can be easily made between alike characters
There is good overall disambiguation of similar-looking characters in Consolas. For example, there are slashed zeroes, meaning the number "0" can be differentiated from the letter "O".
Pro Supports patch that adds Powerline symbols
Con Not free
Con Font size can't be changed gradually
Letter height is the same for 9 and 10, and for 11 and 12 pt. When switching from 10 to 11 pt, letter height changes abruptly (whereas line height changes gradually). This makes it impossible to choose exact letter height on a standard display. Size can't be set to 10.5 pt, for example.
Con Highly aliased with ClearType
Consolas is specifically designed to work with ClearType antialiasing, so it becomes highly aliased when ClearType is not turned on. This can be alleviated to a degree with any basic grayscale anti-aliasing.
As an OpenType relative of Consolas, Inconsolata works well without ClearType (Inconsolata-g being the most popular variant).
Con Small 'L' is too similar to digit 1
You can tell the difference when they are close together, but when used apart, it can be a bit hard.
Con Poor legibility with small font-sizes on non-hidpi screens
Consolas in the 9 to 13 pt range is hard on the user's eyes with any monitor that's 1080 p or below.
Con Italic font is very different
The italic font (often used for comments) feels jarringly different to the regular one - especially on the "g" and "f" and "l" (lowercase L) glyphs.