Only did it once at the land border but I got grilled going into Canada (politely but 20 questions. and seriously, who memorizes their license plate number if it isn't a custom plate?) in the NEXUS lane, and I got "randomly selected" for a car search on the return to Champlain (from Lacolle, QC) which took over an hour. I then got grilled at the counter until a siren went off and they (CBP officers in building) were told to go to "Lane 4", which had a car surrounded by CBP officers with guns out (at which point a green slip to get my keys back was basically thrown at me).
Based on that experience, I am deterred from re-entering the US by land (as a US citizen and NEXUS member) and prefer to fly, even if the end-to-end travel time is comparable.