Gavin,
Keep taking the tablets, mate.

Personally, I have noticed that the performance of the kata actually improves when you know some of the applications. I tend to not go along with the way my club tells me to and I teach applications as soon as I think the student has reached a reasonable level.
On the issue of speed, I certainly don't agree that kata should be performed at bullet speed. It all just becomes a blur and good technique is out the window.
I suppose people that practice kata fast would argue that in real life you would have to move as fast as you can. My answer to that would be that they are missing the point of kata.