The first thing you should know about the NES Classic, aka the Mini-NES, is that it does exactly what it's supposed to do. The second thing you should know is that it's kind of a pain in the arse.
Let's start with the bad part: Nintendo's newest system, a $US60 ($79) box that can play 30 different NES games, comes with a replica NES controller that perfectly recreates the one we all had in the '80s.
Because this NES controller has no "home" or "menu" button, Nintendo has decided that the console's "reset" button will serve the same function. Pressing reset on the box is the only way to switch games, access save states, and change settings.
In other words, you'll want to keep the box next to you, which is probably why Nintendo decided to couple the NES Classic controller with an inexcusably short cable. It's three feet long, if you're being generous, which means that most people will either have to A) get a new controller, B) get an extension cord, or C) dangle an HDMI cable across their living rooms, risking danger to their significant others, pets, and Roombas.
It's a frustrating flaw in what is otherwise a great system, and it's one that could've been solved pretty easily if Nintendo had just added a tiny home button to the controller.
But, yes. The NES Classic is a sleek device. It's tiny, light, and adorable. It's got 30 different games -- some of which are good, some of which are not-so-good -- and it does a fantastic job emulating them all.
You can play each game in one of three graphical settings: Pixel Perfect (which looks excellent on modern TVs), 4:3 (which stretches out the pixels to make them look like the NES's aspect ratio), and CRT (ugly, but nostalgic). You can also set up four save states for each game, which is useful, because most NES games are punishing and unforgiving. As a general rule, games look far better on the NES Classic than they do on the Wii U's Virtual Console.
If you don't have fond memories of beating up Garland or destroying Crash Man, there might not be much for you here. There are some games that hold up particularly well today, like the Super Marios and Kirby's Adventure, but the NES Classic is mostly designed for those of us who feel nostalgic. If you grew up playing NES games, chances are very high that you'll love it. If you've never picked up a Nintendo controller, you might find these games antiquated.
The '80s were a different place. (Inevitably next fall Nintendo will release an SNES Classic, and that will be another story -- Super Nintendo games have all aged far better than their 8-bit predecessors.)
Assuming you can actually get your hands on one of these things, you're in for one hell of a nostalgic trip. Just be prepared to solve the controller problem.