I feel that in single player games, you should be able to do whatever you want. If you want to use a trainer or cheat, have at it, it doesn't affect anybody else. I despise it in multiplayer games, though.

I don't cheat. I can't remember ever using iddqd or idkfa while playing DOOM. It was nice knowing that something like that existed in case I just got stuck.

I wonder how long it will take for cheats/hacks/trainers to show up for Dark Souls. If there was ever a game that is going to need it - that is the one.