I sold my Ju-Ju-Be Between but kept my BeSmall. They have the most gorgeous changing mats and are terrifically practical. I will definitely get some of the Be-Mines in the new prints as I think they'd be great for organising nappies etc in other bags.
But my favourite is my chocolate brown Storksak Emily. It has insulated side pockets that take both bottles or beakers, plenty of pockets , a detachable mini-bag for purse/make-up and lots of inside space. While I was exclusively breastfeeding I used the side pockets for hairbrush and umbrella. I really fancied it in silver too but bottled out on the cost.
If I'm just popping round to a friend, I take one of those tiny M&S simply food canvas bags. Just big enough for changing mat, spare nappy, spare clothes & cup/bottle. Easy to carry with the baby in the ergo too. Mine has a union jack on and doesn't feel like a baby bag at all.