It is nowhere near as slow as people might imagine it to do. I had expectations of a real slow start with it picking towards the end, buy the plot got going pretty quickly.
Alright, the main villain, the Red Skull, unearths powerful device left behind on earth by aliens which people mistaken for the Norse gods (from the Thor movie, naturally) and uses it to give a faction of the Nazi party, Hydra, a huge advantage in the war.
America's only hope of fighting back against this new menace is their new super soldier, Captain America/Steve Rogers. He leads a team of exceptional soldiers against Hydra and their super weapons to stop The Red Skull from taking over the world (OF COURSE!!!).
Believe or not, but the filmmakers were able to give Captain America the same real world feel that the Ironman films had and were able to play this Saturday Morning cartoon plot well enough to make for a two hour film and they did effectively.
The writing is concise, to the point, and so is the dialogue. The acting is top notch, but all the actors in their comfort zones (Hugo Weaving as an over the top villain; Tommy Lee Jones as a tough, smart-lipped military officer), but the actor who truly shines is Chris Evans as the Capt.
I don't know what anyone here thought of him as Johnny Storm/The Human Torch in the Fantastic Four movies, but his acting in this film is a whole other game.
The action is excellent, and there is plenty of it, the special effects were near perfect, the pacing is quick but not rushed.
Obviously, this film is very dramatic, as you probably figured, since this takes place in WWII, yet Chris Evans is returning as the Capt. in The Avengers, which takes place in modern day.
Overall, they took what could have been bad, real bad, and really turned it into something, instead.