I received my STM Small Alley Shoulder Bag earlier in the week, and I really like it. It's got a nice build quality to it.
It's definitely a little big for the 11" MacBook Air, and there is a a little gap on either side of the flap that closes the laptop compartment, but as
entatlrg said, it isn't that bad.
Because it's a little big for the 11" MBA, the MBA can slide around a little inside the laptop section. So, I decided to buy a sleeve in order to stop the movement. It worked like a charm.....now the MBA doesn't move around inside the bag. Plus, the sleeve protects the MBA from those little gaps.
I bought this one from Amazon, and received it earlier today. It only cost $12.99, and it's very nice. It should be at least $30. Solid build, strong zippers, and a nice sized extra compartment to store the power brick, a mouse, or other small items. Plus, it came with a velcro strip to use as a cable tie. Here's some pics from Amazon:
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I really like how the zipper opens up three sides of the sleeve, that way you can just open the top part and slide the MBA out (perfect for inside the STM bag), or you can unzip all three sides and just lift the MBA out.