I will actually take a strong opinion that my subpar grades from undergrad and graduate school are a large factor in why my PhD is going to take a long time. As [David Ketcheson][1] mentioned, quality grades and GRE scores are important denominators for Graduate fellowships. So far the NSF, NIH, and DOE have all denied me fellowships because I have a lowish GPA according to my reviews.

That being said, once you are an established researcher with a paper track record, the grades really shouldn't matter asides being a bragging point.


  [1]: https://academia.stackexchange.com/users/81/david-ketcheson