Thanks for the responses so far.
I think my question might have been misinterpreted slightly. I was looking for stuff to get done
in the next version. Don't get me wrong -- some of the ideas here are very interesting -- but, being realistic, they are not all going to get done in the next release. For example, if I worked on a tutorial then that is quite a big feature so it would probably be the only major new feature in the next version. Alternatively I could do some work on a map editor, but then there would not be time to make a tutorial for the next version. And so on.
So, perhaps I should put the question another way: if you could choose only one thing to be added, what would it be? Or, if you had to rank things in a priority order, what would it be?
Now to respond to some specific points:
Tutorial mode: personally I think this is a high priority, as it would help get new players interested in the game (and we do need to get more players involved). Although, as I said, it is probably quite a lot of work.
For user-created rooms: I was thinking that users would make "room packs" which could then be uploaded to the server (probably after vetting by me, if only to make sure they work properly and don't crash the server and so on). In the game, you would be presented with a list of available room packs, with a check box next to each one so you could turn them on and off individually. (This would probably be on some sort of "advanced settings" tab.) The dungeon generator would then pick randomly (in the usual way) from all the selected rooms.
Regarding more control of the generated maps: This isn't really possible at the moment, it would require some fairly major changes to the dungeon generator, so I probably won't do that for now. I'd rather get the "room packs" working first, I think.
Switch operated metal doors: actually the game already has these

It's just that there are only about one or two rooms that actually use them, so you don't often see them.
More control over scrolls/potions: interesting, but probably not an immediate priority, I would have thought.
Pause option: yes this is a good idea (and should be fairly quick to do) so I'll see what I can do about that one.
Time sensitive switches, and dark rooms etc: This should probably wait until there is a dungeon editor in place, otherwise there will be no way to design said rooms and import them into the game

Companions: an interesting idea, but would need some moderately complex AI so I guess I'll be leaving this one for now. It's an interesting future idea though. It's related to the idea of having "bot" opponents which people have mentioned before. (In fact, if you have "team" games plus a couple of bots playing on your team, then you basically have the "companions" idea right there...)
That reminds me: no-one has mentioned team games yet. How much of a priority do we think this is, compared to the other things that have been mentioned in this thread?