I can't stand it, the see-through look when worn two sizes too small (usually the case), the camel toe, muffin top, cellulite visable through them, everything about it is trashy. I wore leggings once when I was heavily pregnant and nothing else fit me but never without a dress over the top that came to the knee and they went in the bin the moment I popped! However, I do own several pairs of 'jeggings' that are quite thick and I love them-but I still cover my arse when wearing them. It's my, perhaps rather mean, opinion that certain clothes just should not be available in sizes larger than UK 10. They don't flatter the wearer at all, it'd be doing them a favour.
Although I just know that if that happened there'd be a tonne of size UK 12 girls shoehorning themselves into size 10's