That's exactly how my currently Macbook behaves. I could write a short script to turn off/on the WiFi after login, but it's really annoying that you have to do that for such an expensive device.
Same here. Oddly, it always connects immediately at work, but fails in this same way at home, where I have an Airport Extreme router. You'd think if one combination was going to fail, it would be the one with two vendors.
EDIT: This is on 10.9.2.
I don't get the WiFi disconnects, but 10.9.3 has stopped being able to automatically connect to WiFi.
Wake up Macbook from sleep and find WiFi disconnected. Click icon, see only a couple of SSIDs, click the one I want, get the "unable to connect dialog". Click icon again and wait for refresh; now see a much longer list of SSIDs. Click the same one that it couldn't connect to before and it finally connects.