Well, I went ahead and got one. A calico female who I must say has greatly surprised me! So much for being slow and clumsy like I thought a balloon would be! She's very confident, and she swims every bit as fast as my other molly, and doesn't seem the least bit in pain or uncomfortable. She is always ready to eat, and is very friendly, outgoing and personable. So far, no aggression problems with ANY of my livestock, either with my other fish or her, and I have female bettas, platies, mollies and bottom dwellers together. Nice to know they get along with guppies too! I only had to take back one betta because she was a bully, (before I got the balloon molly) but have had no problems since.
I am totally in love with this balloon molly, and wonder if they are all as sweet as she is. She's noticeably fatter than when I got her (2 weeks ago) so I think she's pregnant. Very excited to see what I get, as the males she was in with were dark calicos (she's a light one) and I'd like a dark one, so that's what I would keep if I get a female dark calico. At first, I thought they were ugly, but the more I saw them and read about them, the more they grew on me. And mine doesn't have the overly curved spine like some others I saw do. Maybe that helps? I'm a huge fan of black moors, I had them as a kid, so this is great--kind of like having one again!