I enjoyed this post over on Medium by Matt Cooper who writes about his experience over the last 18 months designing line based icons. For a while there everyone was in a tizzy over whether or not line icons were legible or not though that fervor seems to have died down. Now we’re starting to see some well-executed icons in this style like the one’s Matt has made, which to me show the validity of line based icons.
If you’re curious to see more examples you should check out Designspiration’s collection of line icons. A plethora of icons to inspire your own work.