Wow, that was a fast response!
For some obscure reason context sensitive (or partially restricted actions) keys are generally considered a really bad thing for a roguelike.
This I was aware of, and I think ywgdana provided a nice explanation of why. The freedom to perform a variety of actions with the same set of objects (actions that may not be obvious) is a particular highlight of roguelikes, but not all of them do this.
There's also the fact that although the action is available it often does nothing. I've tried digging in Angband without a shovel and realized, as Yyrkoon said, that it's actually pointless; why even allow it? It's allowed because of how the commands were created.
So, from this I'm guessing that key items need to make sense (or at least be accessible when they should be), and I also need to recognize that restricting the freedom of use on items can be detrimental. This at least provides some guidance on how to organize the commands and possible actions of the game.
Really, what I wanted to do was create a progression of useful items that increased the capabilities of the player (though the capabilities of the player's character could just be improved over time as well). My concern was that it would be detrimental, but actually now that I think of it (and think of how Metroid did this) there was also the notion that the new commands opened up more of the game. It wasn't just that you couldn't get past this wall without a shovel, you could explore so much more of the game with one.
So if I want to go down this path, I'm guessing I need to make a game that has a lot of hidden secrets that get unlocked the further the player progresses through the game (and make sure it isn't tedious for the player to revisit old areas).
On that note, do people prefer the range of uses items have (such as in Nethack, Adom, and to an extent IVAN) or do you think having that makes the game more complex than necessary? Assume the game is supposed to be larger than a 7DRL.