I definitely had a good time in this movie. Even as a comic book movie, involving completely preposterous science and revisionist history, it felt very grounded and down to earth. I think that's because it felt very character driven and character focused.
It also has plenty of action and plot. The whole thing chugs along at a nice pace, with decent writing, acting, and directing. There are good jokes and even a heartache or two. It's amazing how deftly it served up heaping helpings of patriotism and courage without ever quite wallowing in self-awareness or corniness.
I particularly loved all of the period details, especially the over-the-top retro-advanced gadgetry. It wasn't until afterward that I discovered the same director gave us The Rocketeer (another favorite). Recommended.