I wonder if they could increase the limits in some cases. I don't mean time limits, but, for instance, number of digits of sqrt(2), add some sudoku boards, that sort of thing.
For example, my Java solution for SUD is recursive with a simple heuristic, as described on wikipedia (take a square with the minimal amount of choices). It doesn't solve a 4x4x4 sudoku in time (from one of the ACM regionals), so I think I have a lot of room for improvement (it solved 381 in less than 3 secs).
I love these challenge type problems, I should take a look at the archive. I just checked Tanaka's restored imagees, that is amazing.