For those you did enjoy the film, the fact that it isn't doing gangbusters at the BO compared to the first film should be at least a little worrisome. That means that it isn't expanding its audience.
As Crook and ISS and I just pointed out, momentum is very important, especially for movies that are part of a series. If one part underperforms in terms of BO or hype, then the next installment has to work that much harder to get people on board. IM1 built up a lot of goodwill and IM2 hasn't taken advantage of it. So the upcoming movies (Thor, Cap, Avengers, and obviously IM3) will have a little bit of a harder time getting a leg up, especially if it's all supposed to be under one Marvel Universe umbrella.
TF2 did gangbusters compared to TF1 because they simply took what worked in the first movie and made the scope bigger. Doesn't matter if the movie was crap, the marketing made it into a must-see event featuring some sweet money shots and that's all you need to get butts in seats. Now if they can make it even bigger for TF3...we'll have to see about that.

The WOM was pretty bad for TF2 beyond the cool robots fighting.
I haven't seen IM2 yet, but the marketing didn't make it seem very exciting. Mickey Rourke and Sam Rockwell as bad guys are pretty cool, but the trailers didn't show much scope, especially compared to the first one. IM and WM shooting at things? That's your money shot? Alrighty then. You've got to make it bigger.