I don't know that it is a bad idea to half ass the effort on the IR section, but I can imagine many schools claiming they don't factor in the IR score, but then looking at an IR score of 3 or 4 right next to an overall score of 740 and determining they will pass on that student. In other words, I don't think a top b school would think too much about a 6 or 7, but they might be put off by a 3 or a 4, which, unfortunately, are the IR numbers I'm consistently getting on practice exams.
I'm actually using the GMAT Pill right now, but it is becoming doubtful that I will get to a point where I'm confident in my ability to do well on the IR section. I really need to complete the GMAT before the IR section becomes a real factor in the overall score...
You know the biggest issue I have with the IR section is that I believe it is truly a valuable tool for evaluating a prospective student's abilities. I deal with IR-type information all of the time in my current role, so I think it is heavily attached to the real world.