My wife gave me one of these for Christmas.
I've played it a couple of times.
It's OK.
The games are not the original Atari code however - they have been modified slightly - probably to accomidate the new hardware.
I have verified this against my A2600 & cart collection.
Bottom line: it doesn't beat a real 2600 but for about $ 25 who cares.
Never did try try to hack it but it did give me an idea to convert one of my extra 2600 controllers into a PC gamepad.
I'm still in the planning phase on that one.
I'll either have to find an very small gamepad pcb to fit inside the base under the original contact board, or wire the controller to an external box that will house the gamepad pcb.