Was in room 1503 last month, the second building in from DTD, on the first floor. It was a wonderful room, highly recommended. I've been in Congress park 5 or 6 times, Paddock and Carousel 4 or 5 times each...definitely prefer Congress Park. Building 1100-1400 is the closest to Marketplace, but building 1500-1800 is only another 100 feet added to the walk, and actually has some advantages in my opinion...like being closer to the bus stop, closer to the pool, and slightly removed from the main lakefront sidewalk.
Room 1503 was great because it was on the ground floor, at one end of the building where it sits closest to the lake, and the closest point of the building to Downtown Disney's pathway. It was a 'pool/garden' view - but I personally hate actual pool view rooms as I tend to like a little more quiet and privacy - this room actually looked out towards DTD and the lake, through a lovely wooded canopy of trees, with the pool just to the right of the patio, about 50 feet off. So access to the pool was at utmost convenience, but without any of the pool noises or privacy issues. And the patio had a nice covered recess to one side that made it longer than the usual balcony patios and weather-proofed during the rain. Also, since it was at the far wing of the building, there was an exit door by the end staircase just 1 door over, meaning you didn't have to meander the hallways back to the central entrance to get in or out, and with that exit door facing the DTD walkway, it was a cinch taking that walk.
I actually preferred that room location to the lakefront DTD-view room I had at building 1100-1400, which seemed to have a bit more foottraffic walking past the rooms than the recessed 1500 wing.