I recently tried setting up a cron job that I wanted to run every 10 minutes. So I tried entering "*/10" in the minutes field. Which it happily accepted. Then when I accepted the full schedule I saw that it had silently been reset to "0".
My work-around was to explicitly enter each interval "9,10,20,30,40,50". This would have been very annoying if I wanted to run the job ever other minute.
On a related note it would be good to have a "Select All" button for the months of the year, and the days of the month. Either that or default to having them pre-slected.