This is exactly my problem with Ultimate Spider-Man.
To give you a little lecture on story structure, a protagonist's life is more or less neutral until the inciting incident. This event of story radically upsets the protagonist's balance of life, either towards the positive or the negative, with or without irony. For example, the murder of Richard Kimble's wife in THE FUGITIVE. The opening scene of the film, and we're off. Sometimes, the event comes in two parts. The inciting incident of JAWS is one; the shark eats the swimmer and the sherriff discovers the body. We don't have 'slices of life' in between these two events. The incident can come anywhere in the story. In THE LORD OF THE RINGS, the inciting incident is Frodo picking up the One Ring and then Gandalf explaining to Frodo what the One Ring means and what must be done about it. This scene occurs almost an hour into the film. How do you keep your audience interested? Sub-plots. In The Lord of the Rings, we have Bilbo's party. In SPIDER-MAN, the inciting incident is in three parts: Spidey gets his powers, Goblin gets his powers, and they meet. The meeting doesn't happen for more than an hour. To keep the story going we have the MJ love story, the Uncle Ben plot, and the Osborne insanity plot.
Now look at USM.
Ultimate Carnage has the inciting incident of "hero discovers monster". This does not happen until the 4th part of the story. Are there any sub-plots in the first three issues? The closest we get is Connor's desire for a breakthrough. But this has an inciting incident that occurs in the second issue. So in three issues, all we get is one inciting incident for a sub-plot.
Ultimate Hobgoblin is, (as is the general convention for superhero stories: hero discovers villain - hey, it works for Bond) the same. The inciting incident doesn't occur until the fifth part (we assume). What sub-plots do we get? Harry is supposed to have a sub-plot, but it is under written. We don't know anything about Harry, and instead of being mysterious, it just feels slow and pedantic. The MJ/Peter break-up sub-plot would be nice if, emotionally, their sub-plot had changed over three years - which it hadn't. They were in this position three years ago, so it's feels like retreading old territory. The sub-plot didn't start until the third part.
So when you are saying "nothing's happening", I'd have to say you are exactly on the money.
Hero discovers Villain. A superhero story starts with that. If you delay it, by God, you've got to put something in their to replace it... just like Bendis did beautifully in the first 7-issue arc of Ultimate Spider-Man.