Our firewall uses the Windows firewall system so it doesn't add instability to your computer. I was afraid it would sound kind of lame to talk about the awesome firewall when it's more of a firewall manager.
I think the monitoring feature is the most useful thing because you can go back in time and see your network activity for up to 30 days, or of course clear your history if you want.
For Mac there is Little Snitch but for Windows I haven't seen anything that has a "network time machine" like we have and also gives notifications like we do. The way GlassWire organizes the data is kind of unique.
I made this application for myself due to my own paranoia.
Can it import existing whitelists or blacklists?
If there are competing products (paid or free), a comparison would be helpful.