With DDs, I was not a fan of JJB. I tried the Be Tween and I think Be Spicy. I found them heavy and hard to pack without having them look like they were stuffed to the gills (for just one kid).
I have read that the newer ones use a new fabric, so they aren't as heavy. I don't know if that applies to all models or not. It's just a vague recollection I have from reading in their forums.
I now have a Be Hip for DS and I love it. Best bag I've ever had (I've used Skip Hop Dash, Fleurville Sling Tote and various no-name ones from BRU). I thought the vertical packing would be strange, but I've found it suits me perfectly.
mom to DD1 (17), DD2 (14) and DS (9)