Here are some real life, non-promotional pictures showing box, contents, and size.
Box has a sliding flap instead of an adhesive seal, so you don't need to cut anything to get it open.
System, 2 controllers, HDMI cable, and USB to micro-USB with AC adapter.
Controllers are very similar to original 3 button controllers in both weight and balance. D-pad and buttons feel good. Genesis Mini on left, Genesis on right.
Comparison to the 6-button Turbo Mk-1470 (top right) and 8BitDo M30 (bottom) for fun.
Size comparison against original Genesis
Size comparison against Model 2 Genesis
Size comparison against Analogue Mega Sg
So how does it play? Very well. After a quick sampling of a few games, the emulation seems excellent. There is a tiny bit of input lag (on par or better than the NES/SNES classic) and audio lag, but the experience is great. The game selection is awesome and includes a lot of titles that people don't really talk about anymore as well as the usual classics. Everything just works and there is actually a shortcut (hold pause button) to get back to the main menu! It shall sit proudly in front of my TV as a reminder of the days when Sega ruled the roost. Is it worth $80? That is entirely up to you. All I can say is that it offers exactly what it advertises: A very enjoyable trip down memory lane.
Of note, it only includes two 3-button controllers, so the 6-button fighting games are essentially unplayable. This is inconsequential to me, but you should definitely take that into account if you're not planning on picking up one or two third party controllers.