How to make the game truly challenging (?)

So, I've been reading through these forums for awhile now, and I've been awestruck at how much better players many of you are when compared to me. Some of the challenges that people put themselves through seem to be truly insane.

Well, an idea hit me for all of those players craving a true challenge.

The no-pause challenge!

The pause button is a life saver. For groups, it lets you actually manage your party. Even solo, it buys you so many precious seconds as you pull out the right spell, ability or potion. It lets you take a look at the battlefield and figure out which threats there are.

Has anyone ever tried this? If so, I'd like to know if it is as difficult as I imagine it to be.