For as long as I can remember, I've always used a TB bag of some sort for my travels. I'm making an exception with my upcoming trip to South Africa, and I honestly feel like a traitor.
I was at a trail race the other weekend and wound up approaching a woman who had what looked like a very convenient backpack. It had that big "open maw" style of the Smart Alec but it was emblazoned with a Speedo logo. She raved about how easy it was to just throw everything into the bag and how she used it as her main gear bag. She warned me that she'd had it a few years so that chances were likely they didn't make it anymore.
Well, she was wrong. It turns out Speedo makes ONE main backpack (if you're curious, it's called the Teamster, and the large one that she had, has a 35-liter capacity), and they make it in like three dozen different colorways.
Size-wise, it's comparable to the Brain Bag, but it has a waterproof bottom and a shoe pocket, which will work for me for carrying my racing shoes (we're running the Comrades Marathon).
For what it's worth, my main carryon will be stuffed full of TB goodies, like packing cubes. So I'll still have a lot of TB stuff. Just not the main pack.