I've used one before, but never took to the practice exactly. The practice being pouring warm salt water up your nasal passages. The "nasal wash" is a "time-honored practice in the Orient" for treating allergies, colds, and sinus problems, according to my Neti pot instructions.
And indeed, Hybrid-Fat-N-Sassy was shilling for it (she of the Neti-industrial complex) as I complained about my post nasal drip and endless coughing. This is what a Neti user looks like, if they are beautifully lit and apparently not at all unwell:
The part that's missing is the water coming out of her other nostril. Awesome!
It is not a pleasant sensation, but it's doable and the result is that you get to stop breathing exclusively through your mouth for a while. Not bad.