Personally, I think imagetrail is a good thing. It reminds me of the visual disturbances mentioned here:
http://www.pshrink.com/chapman/
Specifically, things like ``Things go too quick for my mind. Everything is too fast and too big for me—too quick to study. Things get blurred and it's like being blind. I can't make them out clearly. It's as if you were seeing one picture one minute and another picture the next. I just stop and watch my feet. If I move, everything alters every minute and I have no control over my legs,'' or ``If somebody moves or speaks, everything I see disappears quickly and I have to put it together again.''
Daniel also seems to have the blocking phenomena down, as well.
I once thought of modifying the HPL engine to incorporate some of these phenomena, to make a character who was literally going insane...but it looks like I don't actually need to modify the engine.
Good work, Frictional!