It works on all levels, standalone, as a sequel and as part of the MCU. As for the latter, there are a bunch of references to the rest of the MCU but more so events that will set up the rest of the MCU from here on out. Apart from Winter Soldier's identity there are two other big twists which I didn't find too surprising but they're still great.

The action sequences are IMO the best in the MCU so far.

And yes @ the mid credits scene.