It took me a little while to really understand the point of Pinterest, but now that I finally get it I am obsessed! I think initially I saw it as just another tumblr or weheartit - a place for endless streams of pretty pictures, which I do rather enjoy, but I didn't really need another one. Where the crucial difference comes though is Pinterest is about categorising your pretty pictures - and as someone who really quite likes organising things this is what appeals to me!
I have a board for my style inspiration, of course, a board full of healthy eating inspiration and another filled with baby animals which never fails to cheer me up! My now rather neglected tumblr was more of a stream of consciousness, but with pinterest I really can see myself referring back to my 'pinboards' for inspiration again and again.
I signed up via requesting to join the pinterest waiting list, which took about a week before I was at the top of the queue and allowed to set up an account. This annoyed me slightly, as I dislike the whole 'invite only' exclusivity that things like lookbook and other websites sometimes have - but a week isn't too bad a waiting time I suppose. Now I'm a member I have some invites which I think I can send out which may let you skip the waiting list (I'm not sure), so if you would like to sign up let me know and I can email you a link.
If you are on pinterest and I'm not following you yet let me know as I'm always looking for more people to follow!