I thought I will write some suggestions for making spoj better.I will update them when I remember something.
1)when someone comments on a problem the problem setter should be notified on his account page. This will help valid queries to be answered in less time.
2)A pm system for communication between the coders.
3)On the status page when I click on the "execution time" link it should go to the page in best answers where my submission stands. Right now it points to the first page in 'Best answers'. But if I am a submitter I would like to see where my submission stands among other submissions in one click.
4)Also please mention somewhere more about how a best answer is choosen. I did a quick Google but couldnt find any link. For example many submissions are with 0.00 time , so how do you decide the best?
