In my case, grad school performance seemed to matter more. I had a mediocre undergrad GPA, but never got below an A- in a structures class. The structures professors took that into account and gave me good funding in grad school. They got to know me in my MS program, which really helped get that first job. Beyond the first job, though, I don't think GPA made a difference one way or the other.
There's been some talk in this thread about whether it matters where one goes to school. In structures, I think it matters tremendously. Many schools don't offer a lot of structural engineering design classes. Guys who took 2-3 classes each in steel, concrete, foundations, and wood (in my experience) have a much deeper knowledge, even 5-6 years down the road, than the fellows who learned those subjects on the job. I have been involved in the hiring process a few times and we gave the school and number of design courses a lot of weight.