Here are a few bugs/issues that nees some attention:
Bugs: 1. The spider lady multiplayer crash. This has been talked about a lot but it's very annoying bug and can break the multiplayer.
2. The legendary armor bug. I've heard that once you upgrade the legendary armor to max and start to recieve coins for completing the collection again, the effect of the armor disappears. A guy on facebook told about this, but I don't know if it's true. If it is, it needs to be fixed as soon as possible.
Issues: 1. Ally stats. It's very annoying not being able to see your allies' stats after upgrading them to 10. Good solution to this would be to create an ally sheet, that displays your allies' stats from health to attack and movement speed.
2. Artifact stats. This is pretty much the same as allies' stas. It would be nice to see how much the artifacts affect your stats, and just being able to see their effects after upgrading them to max.
3. Price the F down the sorceress. Simply put : it's too expensive. Charging 50€ for a character that you don't need and isn't really that special is BS. If it was 10€ I would propably buy it immeadetly, but charging 50€ is too much. You could buy a DS/3DS game with that much money. At least make an alternate way to unlock her, like for example: a hard mode or beating both samurai and zombie campagins (I know the zombie mode will come eventually).