I have a Slipstreamer Spitfire (https://www.amazon.com/Slipstreamer-S-06C-Motorcycle-Windshield-Clear/dp/B000GTUM9O) on my Ruckus. Works fine, except I had to mess with the mounting hardware. For some reason it never held very well for me.

Pros:

Helped keep the country bugs off my face before I rode with a full face helmet

I like the looks

Inexpensive (like $100)

Not super big

Probably gives at least some negligible aerodynamics effect at 30mph.

Does have a noticeable effect on wind buffeting. My head and body don't get "whipped" around as much. Makes the ride more enjoyable.

Cons:

A bit tricky to get mounted properly without it moving around

Bolts are prone to falling out for some reason, even if tightened. I use loctite.