I think it is difficult when you only have a short training session with a new group and you are wearing a white belt. However Aikido is great because the contact is so intimate that you soon learn how good someone is when you train with them. You just have to make sure you train with the higher grades to get recognised (a bit of a philosophical quandry in there somewhere).
Hakamas are useful on courses, as it allows you to tell instantly who the better Aikidokas should be and try and grab them. However there is nothing worse than a crap dan grade, which tends to lower your opinion of the whole club.