I did. Only once though - as my body just would not relax and I got cramps in the back of my knees from squatting - so up down, up down, up down I went. It was very strange. If it wasn't in a foreign country where you can pick up all sorts of things, I just would've parked my butt over the hole and sat down!
End of trekking season is fantastic - the toilets don't get used anywhere near as much as they do in peak trekking season, so they don't smell anywhere near as bad. In fact in most cases, I didn't smell anything at all
Although in one case someone had diarrhoea previously and had missed the hole. This did smell. My iPod in my (zipped up) pocket of my shorts fixed that as my senses were focused more on listening to music than the sense of smell. So that definitely helped
All in all, on the whole (pardon the pun), I don't really know why it's such a big deal...(then again, we go on many 4wd trips quite frequently, so maybe I am used to pit toilets etc *shrugs* )