Here's what their site says about it:
National Harbor is not so much a destination as it is an experience — and we’re committed to providing you with a never-ending variety of things to do. Immerse yourself in the sights, scents, and sounds of our unique waterfront wonderland. From fresh artisan cheese to cinema al fresco to family-friendly fun, National Harbor is your place to play. Come on a whim; stay for the night. We’re right on the water…yet a world away. With all the things to do at National Harbor, you’ll be coming back for more fun in no time.It was a little cold and over cast when we arrived but by the afternoon things had cleared up and it was actually warm.
It is a fun place to go but I'm not sure I'd go there on a regular basis. Once the casino is built I think it will be a really busy place. We enjoyed going up in the Capital Wheel. We did find it odd that there wasn't a shuttle bus to take people from the Harbor to the outlet mall near by.
I take that back there was a shuttle from the big hotel there but it didn't start running until 4pm which we both thought was odd.
One more thing there was some sort of cheer leading competition going on there. I find it a little creepy to see all these young girls running around in their cheer leading outfits. Sometimes they would even break out into cheers while walking down the street. After awhile at the hotel and later at the Harbor itself all you saw were cheer leaders. It sort of made me think of a Twilight Zone.
Here are some pictures from National Harbor.