I liked it more than the main game. I thought the story was less convoluted with the tighter focus on just one antagonist and I loved the entire vibe around the Harlem neighborhood, with the hip hop beats in the soundtrack while swinging through the city and everything. I also liked Miles more than Peter. No specific reason, I just found him even more likeable.

Yes, it's shorter, but that also results in a more streamlined, focussed campaign, I think. Having said that, I'd also definitely recommend both. The swinging has a Mario-like quality in the sense that simply moving around is a lot of fun in and of itself. That's a very rare quality in video games, and Insomniac nailed it.