I visited my fiance in PA while we were waiting for our application to be approved. I brought along a letter from my employer stating that I was on holidays for the length of the trip, a copy of my schedule for the upcoming summer semester, and a printout of my itinerary.
At pre-clearance customs in YVR the officer asked me why I was visiting the US, and I told him that I was visiting my fiance. He asked if I had a return ticket, asked to see my itinerary, and then asked me a few questions about my fiance. He cracked a joke about "how I had it made" (this was after I told him what my fiance did for a living) and I laughed, then he told me to have a good trip and sent me through.
Nerve-wracking, but easy!