People don't think of the graphics as negatively outside of our bubble. I think some actually prefer it.
And while once you start getting into the systems, yeah the game is less casual friendly, but on the surface it's actually far more casual friendly. The auto combo is great, and perfect for get togethers with people don't really want to move past mashing buttons. Every casual I've played with so far has had way more fun with this game than MvC3.
Now if that translates at all into sales, we'll see, but I've been saying for a while I really think this game is far better for the casual plain than MvC3 was. For people that stay on that plain and just fight other people on it, it's legit a blast for that. The casual and hardcore bases will not mix well at all, but most casuals don't want to go further than that anyway.
I'm not too concerned with PC sales, it's to be expected that that will most likely be it's weakest system with no cross play.