This was amazing episode. Everything falls into place, from the interactions of the humans and to the Pokemon. They made use of the best and known qualities of each of the gang and ran with it to create a strong unit. And their teamwork shows. Ash leads while Serena gives suggestions, Clemont does the technical stuff, while Bonnie helps a bit in her own way.
They made use of Serena's history with Rhyhorn racing to help Mamoswine cross the steep incline. Their way in making Clemont's Mamoswine climb the incline was great (using ropes to pull Mamoswine up) and one that I would assume something Brock would suggest, though I wonder who suggested it here. Later, we see Serena's fear of terribly constructed wooden bridges back in the summer camp episode, and you can see how Ash just keeps it together despite being nervous as well. Clemont is once again the healer and medic of the group, but moreover, here he has shown an invention that didn't blow up. Bonnie is still Bonnie which is great since no matter what happens she is still there to be the sunshine of the group.
Pokemon interactions are great as well, Chespin is still his goofy self while Braixen is very dainty and channels her inner Constanza. Meanwhile, Noibat shines again using its echolocation to help Ash and Serena find the hot springs.
Overall a goddamn great episode despite the so-called "filler" people tack upon it. And adding to what Clemont said in the end "Saikou Party", well you sure are, guys, best team ever.