Well, in the case of suffix arrays, it's not the coding in C that makes it difficult or time consuming, the algorithms are quite complicated. The speedup you gain by using clever techniques and efficient data structures isn't in the range of 2,4 or 8, it is in the thousands. For example I know that if you'd use a simple qsort() for the suffix array sorting, you would need weeks for a human chromosome compared to minutes the guys need here.
You could also see it the other way: if you use C and maybe OpenMP, then the simple to implement, naive algorithms might be already fast enough.
