Chris can correct me if I"m wrong, but I think the ORIGINAL purpose of the afterburners is very specific: Making backtracking and such less time consuming and annoying.
I mean, for pretty much ANY of the games of this sort, be it Isaac, NT, Our Darker Purpose, Rogue Legacy, Vagante, or any of the zillions of other games that fit into this genre, one of the absolute least-fun things in those games is backtracking. There's often many reasons to do so, sometimes simple, sometimes complicated and with a strategic purpose, but most players dont like the actual act of travelling through that. Unless your character/ship/thing is very fast, it becomes super tedious!
Now, that being said: I actually kinda agree in some ways with the idea of making the afterburner a little harder to control. I'm just not sure HOW.
There's a few things I think it should NOT be doing:
1. It shouldnt ever be annoying to use in cleared rooms. The idea of having rotational controls come into play would probably cause this. A meter of some sort that empties as you use it and slowly recharges would also cause this.
2. It shouldnt ever be so risky that you NEVER use it in battle.
3. It shouldnt be the sort of thing where you need to use it CONSTANTLY in battle.... see Our Darker Purpose for an example of this one. I seem to recall that Chris in particular strongly dislikes that particular problem in that game.
4. It shouldnt allow for enemy/boss patterns to be broken.
5. It shouldnt make any speed item powerups worthless.
So, those are the things that I personally think should be kept in mind with the afterburner. But I agree, trying out some changes to it, not a bad idea at all. Figuring out what those might be though, well.... suffice it to say, this one's not my job to do, heh. You guys can probably think up some better ideas here than I could, that's for sure. So considering those points, what do you think?