Had my first REAL problem with my '01 X this morning. She turned over fine, but wouldn't start. Checked the guage and had half a tank. Thought maybe it was flooded, but no gasoline smell. Then I noticed that I didn't hear the whirring of the fuel pump. Checked the fuse and that was OK. After giving it some thought, I decided not to just go out and buy a pump, but tow it down to Nissan instead. Man am I glad I did. It seems that there is a recall campaign for the fuel pumps on the '01 Xterras. I never got a notice from Nissan, but it's on the NHTSA website. If anyone is having a similar problem, check the NHTSA site before you spend the $$.
http://www.odi.nhtsa.dot.gov/cars/problems/recalls/results.cfm