Not really - it depends on the choice of fonts and their settings. Most sites look good on my system. Occasionally you get such ones, which look weirdly because they rely on some non existent font, and are rendered in fallback mode, using some generic one. If you want to avoid relying on system dependent fonts, use WOFF.
proxima-nova and Helvetica Neue are not common fonts, so putting them as first with fallback to Helvetica is not the best option, if the font isn't provided as WOFF.
