I'm pretty much just echoing everyone else, but...
1)I'd say more, but in different ways. Undergrad you're always getting graded and having to work on something that's due NOW NOW NOW, whereas PhD work is much more long-term. So, on a day-to-day basis, PhDs probably don't get quite as worked up about what's over the horizon. However, you're competing with the best of the best, and it can be very frustrating to be reminded of this after you've had an experiment fail time and again, only to have someone else publish perfect results and invalidate all of your work up until that point.
2)Anyone who doesn't say research is lying or crazy.
3)I guess technically I probably have a GPA, but I have no idea what it is. Your PhD is basically pass-fail, and what matters down the line is (a)connections/recommendations and (b)papers.
4)3.47. Pissed me off that I missed the 3.5 (I was lazy), but I do great on standardized tests, and so that got me into a good program.
5)To be honest? Exams. I'm really good at memorization. But it becomes a useless talent once I'm finished with grad school. I do pretty well at research, which is more important.
6)Very very weak. I'd say that if you break it into big enough chunks, it might be predictive--in other words, someone with a 1.5 GPA might be a worse researcher than someone with a 3.2, but you can't say anything about two people with a 2.9 and 3.8 respectively.
7)You'd better be doing it for the right reasons, and carry no delusions about making lots of money, winning a Nobel, or being hailed as a genius by greater society. Once you have realistic goals in mind and have forgone materialism (or gotten a rich godfather), it's worth it. Many things in life are impossible to achieve without a PhD.
8)Leave a legacy. I may be a tiny cog in a giant machine, but I want to be one that is fulfilling a vital role. One way or another, I want to permanently improve the scope of human knowledge, inspire others to achieve, alleviate suffering, and improve myself while I'm at it.
Can you tell I'm a first-year?