As far as using the devices for their normal purposes, I normally don't use them until I have beaten a game at least once. There are some rare exceptions, such as Battletoads and Amagon, where I was never able to beat the game without help from something like the Game Genie, but for the most part I tend to use them only after finishing the game without them.

I think cheating in single-player games is, well, fair game, as I've always been of the philosophy that if you buy a game, you should be able to do whatever you jolly well like with it for your personal use. Whether it's cheating because you can't get past a certain obstacle, or to save time, or simply to mess around with the game's code, I say that if it gives you enjoyment, then no problem. Some people like challenges in their games, while others like to coast through. In fact, it kind of ticks me off that the current gen consoles don't allow for conventional cheat devices, what with their multiplayer/achievement/firmware updates focus.

As for my take on cheating, we didn't think of it as cheating. Sure, we'd use it to beat a game we couldn't beat before, but we saw it more as a neat hacker tool, a way to get the game to do things it wasn't supposed to do. Unlocking test or debug areas of the game, creating graphics and sound glitches and other strange behaviors. I don't remember doing anything too exciting but it made games a bit more fun in an entirely different way.