Generally all of them perform quite well, but there is always room for improvements :-).
The greatest pain every year is filling up evaluations for more students - every each of them starts with same questions for mentor (eg. how many GSoC did you participate in or how much time you spend on GSoC). I know I can copy and paste answers, but still this looks like something not necessary. Also some information is probably already known to Google (eg. in which years I did participate in GSoC).