It does depend where you sit but even the worst seats there aren't really too far from the track. The bad seats are only "bad" because they're in more boring sections of the track or are too low to see very far.
Unlike most ovals, IMS is so big that you can't see all the way around it. The best seats are in the upper rows or "penthouse" of turns 4 and 1 as they can see all of the front straight, the turn in front of them, the next turn up the short chute (the two shorter sections of the rectangles are called the north and south short chutes) from them and can also see pit road. These seats are typically very hard to get unless you buy them from a broker, in which case they are typically very expensive. The best seats for the money in my opinion are the North Vista, South Vista, Grandstand G, and Grandstand J. The best seats are in Grandstand E, but as I said, it's very hard to get in there.
I do not recommend sitting in the Tower Terrace or Pit Road Terrace unless you really like seeing pitstop action. The Pit Road Terrace in particular has a lousy view of the track and you can't really see any of the corners.
I bring binoculars to the track but I rarely use them.