I love 'em. There my little friends, and bring me down when I'm spinning and calm the nausea. But everyone is different, they don't suit everyone, but they're worth the try. I believe they are quite safe, even in large doses.
One thing I have found is that most cinnarizine tabs dissolve in the mouth, under the tongue or lip. I quite like the taste, the trade name version (stugeron by jannsen) are slightly sweet, but don't dissolve quite so easily. Most generic versions are less sweet, but are not unpleasant. This potentially speeds up absorption, a good thing when really dizzy.
There is a theory that not only do they reduce the nausea and spinning, but over time affect the 'micro-circulation' blood flow to the inner ear, so are supposed to be preventative as well, in a similar way that Serc is supposed to work.
I have not used them in this way.
I used to find they caused drowsiness, but I don't notice it anymore.
ps as chris says driving is not recommended when on cinnarizine, but it's not safe whilst dizzy either. I have on occasion taken the maximum daily dose, they helped.