not recommended
It is very small and light, controllers seem flimsy and breakable. To quickly summate, it IS cheap, but you seem to get exactly what you pay for going by my own experience and other reviews here.

Felt ripped off
Well I got the Twin Pad Player but have felt majorly ripped off, I mainly purchased the item so I can play cartridge games as well as having some other games built in. The built in games work but the system shuts down every few minutes which is a joke. Also no matter what game I try to play from cartridge all I get is a black screen.

Sound Problems but good value.
2 of my games didn't work, namely Sonic 3 and Toy story because of the lockout chip, and a few had graphical problems.
My only major gripe however is the music and sound effects are off key and just sound wrong. It seems they used a different sound chip or something. I'll have to play those on my original megadrive...
The onboard games are fine and work well.
I would recommend this to anyone that wants a portable mega drive, as it is very small, but not someone expecting a perfect replacement sega as it is not that at all.

Excellent!
It's cheaply made, sure, but it's a fully working, new, licenced Megadrive!

Unlike the other reviewers, I had more success with the games I tried. I tested it with around 30 titles, some each of Japanese, US and UK origin, and only had two problems. One was the UK version of Street Fighter II SCE, which worked but crashed once during a fight, and the other was with the Japanese version of Ghostbusters, where the main character's graphics were corrupted. I then realised it was still on PAL mode, and after switching to NTSC Ghostbusters played file.

Also make sure you clean the contacts on your cartridges! I had a few fail to work until I did so. Not surprising really as some hadn't been touched in 10 years or more.

Great deal, some bugs.
The Presentation is nice, the system comes with a manual in both Chinese and English. The controllers feel nice, but the cords are a little short. The machine feels well constructed, but is very light weight, so, you can expect for it to slide around a bit during play.

The built in games are nice, not amazing, but they aren't the bottom of the barrel either. For cartridge play, I find the slot to be a little big, so inserting a cart takes some wiggling. I guess this is because it needs to accept a bunch of different formats. Some people have reported graphical errors on certain games, but the only problem I've seen was with Sonic 2, where the character sprites are messed up. Another problem on the technical side is that there are a few old games that can't handle the six button controller, and behave in weird ways. I have a copy of Forgotten Worlds, and with the six button controller the game starts with the game over screen, and that's all you get. The original six button Sega controllers have a mode switch which disables the extra buttons, but the AtGames controllers don't have this. This means that some older games will be unplayable. Don't fret too much, as you can hook up a classic Sega pad to the AtGames console, and hopefully get around this.

Even with the technical issues, the price makes it hard to beat. With 20 games built in, it works out to about $2 a game, which is cheaper than you'll find Sega games pretty much anywhere...