Regarding GPA

first is all but required and second is recommended

Obviously, the higher the better. How much better? That's up to the firms to decide, but it only helps you. Worry less about the difference in gpa and more about your overall candidacy.

Sorry to get a bit overboard. What about a difference less than 0.5? Obviously i know the higher the better, any ideas?

You are a bit overboard.

What you probably want to hear is, "oh noo it doesn't really matter. you are equally competitive as the person with gpa+0.05 or gpa +0.1." This might soothe your ego or self-consciousness for a short while, but the bigger picture is what's important.

The reality is that no one can meaningfully tell you how much of a difference it makes between 3.7 and 3.75 or 3.65. No two candidates are perfectly alike, so gpas vary across the spectrum. Obviously there is a weight towards candidates with higher gpas, but at the end of the day, the common denominator is not gpa but rather a strong work ethic, likability factor, and interest in the job.

I had a 3.7 and I was snagging interviews and superdays without a problem. Worry about getting the interviews and the rest will take care of itself.

For targets, once you pass a certain cut-off, people are more interested in what else you have beyond good grades. In my eyes, there's not much difference between a 3.5 and a 3.7. Considering you're competing with the best of the best at a target school, both are respectable. If the 3.5 candidate is good for the group and company, he would get hired. Remember, you're not applying to Law school or PhD programs; if you can make money for the company, you're in.

If you're from a non-target, I would imagine that GPA matters a lot because you pretty much have to be one of the best from amongst a 1000 candidates to even get any face-time with an interviewer.