Thanks for the tip, SaturnGuy.
http://www.twitch.tv/hyperkingaming/b/491644664
I'm watching a video on twitch right now that Hyperkin uploaded two days ago.
This post is going to be very stream-of-conscious writing as I'm watching the video as I type.
It shows Sonic & Knuckles running on the Retron 5. I'm very familiar with the old-school Sonic games so I was hyper-aware of any differences on the Retron 5 compared to the Genesis. There is an on-screen menu that allows the user to adjust the video filter, add scan-lines, or load save states. Despite this, I definitely see dropped frames in the roll animation and the fire animation. The music sounds good (not perfect, but good). In fact, the music is much more accurate than the "official" firecore clone. Some (not all) of the sound effects are off pitch. I have seen the video freeze up for a moment or two.
Next, Hyperkin tried to load an "unknown" game boy cartridge. It didn't load on the first two tries. On the third attempt, the game did boot. This cartridge turned out to be PoKemon Trading Card Game. The video plays in full screen (4:3) without a border on the top or bottom, just black bars on the left and right. The image does not look stretched to me at all. It seems there is a speedup command that the player can use to make boring parts of the game go by faster. This does not require the on-screen menu, so I assume it's mapped to one of the buttons. I have never played Pokemon Trading Card Game myself, so I cannot compare this version to the original.
Next, Hyperkin Loaded Duck Tales NES cartridge. Duck Tales loaded on the first try, but the video stuttered badly. Switching the video filter from "hq2x" to "lq2x" seems to alleviate the video stuttering. I'm speculating that the "hq2x" may be progressive whereas "lq2x" may be interlaced. It's hard to say for certain. It looks very easy to load a save state in case of game over.
Next, Hyperkin loaded Mega Man X for SNES. The picture looks clean and crisp. The video quality is better than my SNES through composite. Despite this, there is definite video stuttering and artifacts. Once again, adjusting the video options alleviates this problem. It seems there's no single perfect video setting. You'll have to decide which option works best in a game-by-game basis.
There are more vids on Hyperkin's channel for me to check out. I'll take a look at those later and report my findings to you.