I've survived a few nights on homemade trail mix, which besides nuts included M&M's, raisins, and sunflower seeds. It was fast, allowed me to ditch cooking stuff, but it got boring real quick. We found ourselves picking out the M&M's and raisins.
That said, I rarely cook when backpacking and bring much more variety, including heat'n eat entrees, tortillas, sometimes fresh fruit. I figure the fruit is about the same as carrying more water.