Considering that this is the culmination of everything they've been building up to since the appearance of the tesseract in Captain America: The First Avenger, I'd say I'm pretty hyped. They have to cover a number of long looked-forward-to moments in this, such as the reveal of the last Infinity Stone, the unification of the Guardians and the Avengers, the revealing of just why Thanos is to be feared so badly (I bet he kills an Avenger before even getting all the Stones, and Vision dying doesn't count since that seems kinda obvious, seeing as he is built around the Stone in his forehead), etc.
Remember that the most powerful Marvel protagonist to date, Dr. Strange, will have to have a key component of that power removed, as the time pendant he has is actually one of the Infinity Stones.
Finally, I'm actually pleased that they dropped the idea of two Infinity War movies, because that worked oh-so-well for the 2nd and 3rd Matrix movies. I'd much rather have a 3-hour self-contained story than a 4-5 hour story artificially split down the middle at some sort of cliffhanger/resolution moment into two movies.