Not from being upside down. I'll get a headache if I spend too long upside down, but I don't get dizzy from it.

I do get dizzy from spinning -- well, I'm fine while I am spinning. It's when I stop abruptly that I get very dizzy, as it's a mismatch of data from my eyes vs. my inner ear that will make me dizzy. As long as they agree, I'm fine! When they don't... blegh. (This is also the underlying reason that people get motion sickness -- their eyes and their ears end up disagreeing one way or another as to what is happening and that is very upsetting to our nervous systems.)