You guys are all using "should" in the place of "I want it to". Just pointing that out.
They are somewhat interchangeable. We said "should" in the sense that "this is how I think the game should be", essentially saying, "this is, in my opinion, the way the game would be the best".
Not all that different from "this is how I want the game to be".
Maybe there could be different skills that could be learned.
There are many games I want to see stuff like this, but I'm not sure if it fits Delver, though. It's not a long, complicated, campaign-like experience like some other roguelikes are. I don't think I'd want to do smithing and stuff in it, it's only 8 levels or so after all.
Dungeons of Dredmor and Crawl both have skills, but they are both long enough to justify character progression features like that.
I'm a sucker for any game that compliments combat-heavy gameplay with non-combat skills to help you through the levels (D&D skills like dungeoneering, disabling traps, dispelling magic to open magical locks... *drooling Homer sound*) but I don't think Delver could utilize them to the fullest.
What skills did you have in mind?