So far my impressions are as follows,
NES- is a mixed bag. Just an average NOAC. I'm OK with it.
Sega Genesis- Rich colors, not sure I like the S-video. The audio is where it is disappointing to me. On most of the games that I have played on it so far, the music is set at a very low volume. Lightening Force is silent when it comes to the music. (I can't believe I am saying this) The RetroGen has got a better (maybe if I stuff a rag into my mouth) sound chip. And I would rather play my Genny games on it. (no, no I can't believe I said that)
SNES- This is the Gem of the system. Can't complain so far with this one. Still not sure I like the S-video. Donkey Kong was nothing but pixels, had to switch back to the composite video.
Even with its problems, I like it. I know clones are not perfect. Original controllers are the big plus here. You are not going to enjoy your experience without them. Some games look great with the S-video, it just depends on the game and how it depended on the scan lines for its appearance. I really like having all three systems in the same space as a SNES console.
PS: I know why they chose the Sega chip, it has a better compatiblity than the RetroGen.