I just played 3 levels in Mega Man 5 and it's not bad. It's totally playable.
The graphics are really crisp. I also like autofire. It's very useful!
Just beat 2 without a single noticeable issue. All in all, I think it's a great collection! Love all the museum stuff, especially the full Japanese manuals.
The games also look absolutely perfect. This is how I wanted VC releases to look, Nintendo! Not the ugly stretched out faded yuckfests we got!
I bit the bullet and bought the eShop version, so I'll throw my thoughts in here as well.
So far I don't see any constant Bloodborne style frame skipping. I'm eyeballing this by tracking small moving sprites, like buster shots as they travel across the screen. On static screens they move completely smooth, which to me says the game is rendering fine on a base level. Nor have I seen any screen tearing during gameplay.
What I do see is occasional slowdown that causes some frame skips. I think the most obvious example is on a stage load screen. I also do see the terrible skip/tearing on the credits screen, which is far worse than anything I've seen in actual gameplay.
As for input latency, if there's any it's minor and difficult to discern. For my part I felt it played well. Nor did I find any audio bugs, although I've only played a couple of stages of MM1 and a couple of stages of MM2.
I'm not a Mega Man expert. I've played the series off and on since the NES days, on a variety of systems and emulators. So I'm not using a strict NES-perfect emulation standard as a reference. All I can tell is that it's enjoyable and plays well enough.
As for the rest of the package, it's nice. I like all the extras. The challenge modes are a really nice "NES Remix" sort of thing. The museum mode, music player, and concept art are all fantastic. I think I spent 30 minutes just looking at concept art and NPC descriptions.
The "VC" style menu is nice as well. You can have a save state and reload quickly enough. Buttons are completely remappable. You can turn the UI artwork on or off. And so on. It's full featured enough that I don't miss anything going from the VC versions to this.
So, yeah. I wouldn't hesitate to recommend the eShop version to anyone. At $15 I think it's a good deal.