I lived in Pioneer territory, not Desert Wind territory, but sometimes boarded at a (semi)civilized hour in Salt Lake rather than in the middle of the night in Pocatello.
My recollections are mostly the same as what was previously posted:
Yes, the odd zig-zag move to get the CZ in and out of the UP station in Salt Lake City despite arriving on Rio Grande and departing on Western Pacific meant that you parked for a few minutes in front of the Rio Grande station. (In front of it, in the middle of a city street, not behind it where you'd expect a train to park.) Moving into the Rio Grande station in 1986 or 1987 or thereabouts was a big improvement; purely coincidentally I happened to be in Salt Lake for something else during the grand opening festivities. They had a nice exhibition train parked there, the whole bit with balloons and hot dogs being given out, etc etc.
My first eastbound ride from Salt Lake, we had only the CZ dining car. Both the Pioneer and the Desert Wind dropped their diner and their coach-baggage in Salt Lake at that time. The one and only time I remember Idaho ever being interested in Amtrak was in the late 80s: there was a bit of a clamor along the lines of "there are 2 engines, 2 diners, and 2 or 3 coaches sitting in Salt Lake doing nothing, 16-18 hours a day. Run a day train from Salt Lake to Idaho Falls with them instead of just letting them idle!" But it never happened (which probably means Amtrak asked for a subsidy and one or both states refused.)
Whenever I saw the Pioneer, Desert Wind, or CZ in the early/mid 80s, they were all-Superliner. Sometime in the late 80s, the Desert Wind got a Hi-Level dining car and started running it through to Chicago. The crew called them the Chicago Diner and the LA Diner; they handed out dinner reservations starting from the end of the train nearest each diner. We would walk to the back to request a LA Diner reservation, partly for novelty, partly because it meant being on the last car of the train and getting a fine view forward on curves.
I don't remember there being a buffet counter / serving area, but I may not have had the chance to look, especially if it was at the far end of the car (the LA Diner being the last car on the train, you didn't ever walk all the way through it.)
I had the general sense that immediately after the Superliners were delivered, there had been a plan to retire all the Hi-Level equipment, and it was put back into service in the mid-80s to increase capacity. I liked the Hi-Level coaches (mostly saw those on the Starlight) and diners at least as well as the Superliners. They were beautifully refurbished inside. But crossing between a Hi-Level and a Superliner did involve stepping over strangely tilted metal plates between cars.
My last Pioneer ride was one of the neatest - we were several hours late, so I got to have lunch instead of breakfast going up the Front Range out of Denver; had "night" from about the UT-CO border to just after Salt Lake; and got to see the Bear River and Portneuf River canyons in daylight before disembarking in Pocatello at 9 or 10 AM instead of 3.
I never got the chance to ride a Seattle-Denver Pioneer. Partly that was the Colorado scenery being better than Wyoming, partly that was me moving to Alaska in 1993.
I do remember thinking, when I idly sketched "ideal Amtrak plans" in notebooks, that I wanted two daily trains, one via the Rio Grande to Seattle and Oakland, splitting in Salt Lake, and one via UP to Los Angeles and Oakland, splitting in Ogden. This was possibly just my selfishness wanting a one-seat ride from Idaho through Colorado... but traffic to and from Salt Lake was a biggish part of the Pioneer's business. If I were limited to one daily train east of Denver, I would have it be the Desert Wind, not the Pioneer, that split off in Denver, so that all 3 trains passed through both Denver and Salt Lake.
