for me,i think it is.
but for example if both want to go virgin because of the religion they believe in,i dont see a problem ( and only if you dont find then that one might be...gay..)
but let me explain why i think it is really important:
sex is a way of loving.a very intimate one.there is a special intimacy that only comes from sex you know...and you will only find if you both have that special chemistry when you do it!
imagine that after you marry,one partner is sadomasoquist and you are a quite shy and more into the "regular" sex..

what will you do???and if you didnt had sex before it,you both will only know it when it is too late.....if i were in that situation i would surely regret not to have found it sooner...