I saw an article the other day about this, let me check my history real fast and I will get back with the link
My ex gf wears them all the time. She loves them and never wears socks with them, always barefoot. Thinks they are the greatest, comfortable, not too hot, etc. You should try them out
Depends on the style. I've had several different styles over the years. Some are comfortable, some will give you blisters no matter how often you wear them. Your feet will sweat in most of them. Smell wise, I rarely get foot odour so it's something I can't comment on. The only pair of shoes I ever got foot odour in was a pair of 'breathable' runners so all I can say is if you are going to get stinky feet, you'll get stinky feet regardless of what you are wearing!
I worked at Michael Kors and they had a few jelly flats. My opinion personally is they make your feet sweat and they smell weird. Don't buy unless you want to wear them in the water. That's what they're best for.
They make your feet sweat and they aren't that cute or versatile. I haven't seen a pair of Jelly flats since the 90's.