I think the old entrance is a better route into the park because of the variety of habitats it spans and the way the you approach the park with a the massif introduced at a distance across the southern steppe. I have never had the opportunity to take my time along this route as we have always been in a hurry to get to the park and my observation of what appeared to be a Black-throated Finch in the grasslands just beyond Cerro Castillo from the window of the moving bus only make me want to come and spend a lot of time exploring this area more.
The weather this day was pretty good for patagonia - not too windy and mostly sunny. There was lots of water in small ponds along the road and we saw many Chilean Flamingos in places I had not observed them before. Andean Condors and Black-chested Buzzard-Eagles floated right above us at one stop and we saw many as we drove towards the park entrance. At the overlook above Lago Sarmiento, where we stop for photos of the northeastern end of the park, I wandered across the road to see what birds I could find in the shrubs along a small drainage next to the road. I immediately found an obliging Mourning Sierra Finch and shortly after that a Scale-throated Earthcreeper hopped on fencepost with a millipede in its mouth, then flew to it's nest hole built into the road berm next to me. I managed to get a photo of the bird as it emerged a short while later with a small rock in it's bill.
We intended to make our way to Laguna Azul after a stop at the waterfalls along Rio Paine but a flat tire on the bus forced us to scrap the Laguna Azul portion of the itinerary. We did get to the waterfalls on the Paine River and found a nice male Torrent Duck sitting on a rock in the middle of the river above the falls. I like this area of the park, including Laguna Azul, because it isn't as heavily visited as other areas of the park and there is a lot of wildlife along the road to Laguna Azul. The downside is that you have to backtrack to get to the rest of the park, probably the main reason it does not have as many visitors.
After our visit to the waterfall we headed through the park to our hotel at Rio Serrano for a late lunch and a free evening. I wandered around the hotel and found a few birds including a Dark-bellied Cinclodes, Ashy-headed Goose, and a Flying Steamer-Duck.