Very usefully.

I love it, I use the user-agent switcher because sites like Roblox believe firefox is "suspicious" and will serve you 10 Captchas if you are on Firefox

excellentai dudes and dudettes

Works in Zen too! :)

The only user agent switcher I've found that reliably works. Allows you to apply custom user agent to a specific domain. UI is simple and easy to understand.

The best user agent switcher. Buffering on Youtube magically gone. Compared to using FF by default that YT will buffer every 10 seconds.

very good at its purpose