My issues have been on an MV1. Super Dodgeball does reset on me, yet when I use the same cart on my MVS converter, I can play SDB for hours with no problems. I definitely wouldn't say anywhere near 80% of the games reset for me. I've also experienced no slowdowns. I'm inclined to think that's user perception, or that perhaps they're playing Metal Slug 2 (or another game known to have slowdowns, like Viewpoint).
Who here's not using an MV1?
For the voltage thing, you don't just "turn up the voltage", of course. You need to test with a multimeter at the jamma edge, while the game is running, and make sure you're getting 5v. I believe the acceptable range stated in the manual is anywhere from 4.5v to 5.5v, no higher, but don't quote me on that. Some titles may draw more power than others?
It's definitely important that we weed out the actual problems from those that stem from user misperception, like the "Viewpoint sounds funny" issue.
Edit: I've had no problems with SVC Chaos, which were you using? Also, I haven't tried MS3 yet, but I played Metal Slug and MSX from beginning to end with no problems.
The bottom line for me is, even if every single game doesn't work 100% at this point in time, it was still worth what I paid just on the strength of the games that do work. If we can pinpoint the problem with getting the other games to work, it's an even better value. I definitely have no regrets about the multicart. Being able to play random-ass games like Driftout and Power Instinct make it worth it to me.