I don't need it for my wheels, but for the other cars I take care of I do. They go for awhile without any cleaning and by the time I get a chance to wash them, the wheels are usually pretty filthy.
I like to spend as little time as possible cleaning wheels as that's probably my least favorite part of washing the car. Whenever I use my Meg's wheel spoke brush, the nasty gunk from the wheels gets sprayed onto my arms, legs, face, clothes and sometimes it takes a 2nd shower before the stuff comes off my body. That's why I'm still debating on getting Wheel Brightener as I know about the health concerns but it'd be nice to have a product that for the most part is a true spray and rinse.