I just spent the past couple hours with the system and am really enjoying it. It does have a little lag, compared to playing original consoles through a X-RGB Mini, but it's very minor and you actually adjust to it after a few minutes of playing a game. It's a massive improvement over the Retron 5, which I've found makes certain games completely unplayable. There wasn't a single game I threw at the Retro Freak that I didn't feel comfortable playing.
I ended up playing carts for NES, SNES, Genesis, PCE, TG-16, GBC and GBA. Everything I threw at it worked perfectly. I even quite enjoy the controller it comes with. It's not perfect and the d-pad is a little 'clicky' for my taste, but it's what I used to play all the games and it wasn't until I turned the system off that I even thought about using an original controller using the included adapter.
I'd actually be very happy to recommend this system to anyone interested in it. It might be a little on the expensive side, but I feel that it's a pretty good value for its performance and its ability to dump your cart collection to a microSD card. I have a feeling this system will be getting a decent amount of use going forward.