Stick with the "courteous" preset if you don't understand Rated 4 out of 5 stars
If you don't know the implications of changing network settings, then you shouldn't change them. This is not a magical Go Faster extension, no extension can do that. The "turbo" setting may open too many connections, and some websites or networks WILL throttle or block you if you open too many connections at once. It's not the extension's fault if you misuse it.
The developer should consider removing or renaming the "turbo" preset, and making "courteous" the default setting. That's the reason behind the "MAEKS MY FIREFOX SLOW!!1!" negative reviews.