Perhaps the best way to close this column is with something I once heard attributed to Stu Card, a pioneer the field of human-computer interaction: "Grad school will be the best years of your life. Having said that, get out as soon as you can."
You will question yourself. You will envy your friends who've graduated from the program and are now working as a professor, or for Google or for MSR. You'll look around at all the new grad students and realize you don't know their names.
So the quote is right on. Enjoy your time, but get out as fast as you can. :-)