Thanks to everyone who posted here for all the great 161-in-1 info! I finally sprung for mine and am loving it. If it just had Shocktroopers, Sengoku 2, Nam 1975, and Super Spy I'd consider it perfect.
I've read the entire thread and I only have a tidbit of info to add that I don't *think* was mentioned:
I'm running mine on a 4 slot MVS cab and I found that holding 1p start will not go back to the menu if the memory card is inserted. You can still us it to save/load games, just have to remember to pull it before trying to go back to the menu.
Also, I haven't tested this throughly, but it seems that so long as I remove the 161-in-1 cart before I put another cart in, the dip setting for that cart and the 161-in-1 are preserved fine. All dip hell does seem to break loose when the 161-in-1 is inserted at the same time as other carts.
I'm curious if anyone found any particularly bizarre/entertaining/useful hack version in there. I particularly appreciate Sengoku 3+ for the unlocked characters. But more often than not I can't even tell what's changed, like in Last Blade 2 Easy?