Thank you all for the responses. "Rough" may be a bit strong to describe what the truck does. Small, but noticable, vibration when idling in drive is probably more accurate. I had a 96' 150 and it purred very quietly. So, maybe I'm just used to my old truck.
Having said that, there is an issue that I'm trying to figure out. Shortly after I bought the truck it stalled as I neared a stop. I took it back and they replicated the problem, though it didn't stall--the rpms dropped to 490. Even after they flushed the fuel system and said the throttle plate had a lot of carbon build-up, the engine noticably labors as it shifts into low gear. It doesn't feel like a tranny problem, it feels more like something in the engine. The odd thing is it doesn't throw any codes, even when it stalled. I'm going to take it back and see if they can solve the problem.

Ed