For all intents and purposes, this it just like a Gamecube controller; it's a solid, reliable controller, but isn't restricted by a cable like the original. It works absolutely perfectly for Super Smash Bros. and is leaps and bounds ahead of using the Joy-cons. It's very energy-efficient too; the included AA batteries lasted me just under 2 months of almost daily use.
However, I did notice in games like Breath of the Wild and Super Mario Odyssey that I turned right slightly when trying to run in a straight line. I can only assume the octagonal hole the left joystick sits in was accidentally molded/cut at a slight angle; no more than a few degrees though. It's not a major problem, but probably something worth mentioning.
Overall, I'd absolutely recommend grabbing one of these controllers, especially if you're an avid Super Smash Bros. player.