It was a blast getting to listen to James, Johnny, and Gui really get into the intimate meat and potatoes that makes Shovel Knight so good. Although you folks didn't use the term I've heard to describe the phenomenon, the miracle of iterative learning opportunities is something I immediately recognized.
One they had going on during the PAX 2013 demo of King Knight's stage was that room where you come up the ladder and there's a long walk around the room to get up to where the wizard enemy is, and that gives the player the chance in that controlled environment to see the wizard charge up his little hadouken fireball and toss it out without getting punished. A good example of this (Bringing it back to RetroActive) cropping up in Mega Man 3 is that any given stage you go to, the first time you encounter a Hammer Joe in a level, it is up on a platform that is too high for Mega Man to get to before he has a chance to throw his hammer once. (except for the one in Hard Man's stage, but given that you have to figure out to deploy Rush coil as soon as you get in the room to jump up there before he has a chance to throw his hammer to be able to take a cheap shot)
I find almost all of Shovel Knight's Relics to be quite powerful and useful, with the Phase Pendant and the Propeller Dagger, and the Horn being the three I go to the most, but the Alchemy Coin, Anchors, and Chaos ball being pretty common pics for the right situations as well. They all have quirky properties that make them pretty ideal for quite a few situations even if their use is not mandatory. I do wish there were maybe a couple more optional stages predicated on their use, but I'm pretty satisfied with the most of the relics.
Actually, to refute another point that was brought up, the Boss Rush at The Tower of Fate: Ascension is really, REALLY kinda brutal on the New Game + mode where all the food under the platters has been replaced with bombs. that's the point where you have to at least either be good at the boss patterns or know the properties of the relics well and have plenty of Ichor with you to endure that mess.
Regardless, I'm with Neal and Zack on this one. I'm enamored with shovel knight's design. it reminds me of some recent fan games that I love but will not name because I feel like I compare things to that particular fan game all the time and try to plug it whenever I can.