Follow up - Here's the details and photos of the drip as I discovered it.
As mentioned, it was coming in the lower left corner (driver's side) of the windshield in back of the dash and only apparent with the pillar trim & handle removed. The black windshield adhesive had formed a glob there and the water, as it entered a bit above there, ran down over the glob and then dripped off of it, forming a small stream of water down the left interior and then down to the driver's side kick panel area.
Here is the drip area entry point: http://flic.kr/p/dtcuTb
And a bit closer: http://flic.kr/p/dtcuSA
You can see in the close-up that the glob of windshield adhesive/sealer (not sure what they call it) is sort of a pea shape here and the water is running across it and off the right side and down.
Here is the area behind the kick panel: http://flic.kr/p/dtcj2P
Circled in yellow is the drip trail which looks like a faint brownish line streaking downward. It was dripping off the blue crimped ground wire connector at the bottom. This is a pair of ground wires somebody cut off from an aftermarket anti-theft system that I asked to be removed when I bought the truck. Below that is a towel I had on the floor (bright white).
I was not certain *exactly* where the water was coming in, but two places in particular caught my attention on the outside. First is this close up of the edge of the driver's side cowl at the edge of the windshield: http://flic.kr/p/dtcuRE
That gap sure seemed ominous as if something was supposed to be there and had worn away. I filled this with silicone. The passenger side did not have a gap like this, there was some material there. I put silicone over there too for good measure.
I also found the rubber surrounding the windshield seemed to have a bit of a gap up by the roof on the driver's side so I siliconed that as well, thinking that if a significant amount of water could run behind there, it would flow down into the corner where the leak was: http://flic.kr/p/dtcuQW
I also found this in similar condition on the passenger side and siliconed it as well. I also siliconed the inside corner all around the drip area and all the way up the left side along the pillar.
Rain & snow came through the day after I did this and there has not been any drips since. There WAS, however, a bit of condensation under my feet at one point (under the carpet). It was not due to any drip but seemed to me to be a combination of: snow that got under there with the sill still removed; and/or because it got really cold out while running the heat inside. If so I don't know how that would ever be prevented. I'm thinking of putting some 2 or 3 mm plastic under the carpet pad there as additional barrier to keep any further moisture from wicking up into the carpet padding.