64gb is more than sufficient for a casual computing experience.
yes, you wont have space for your libraries of music and videos and other large media. But thats not the intention of this device.
For your casual user, Web, Email, facetime, chatting, your odd download or two. Heck, i even have World of Warcraft installed on it fine (with 20gb still to spare), it is more than sufficient.
my primary use of it is around the house. When i'm there, I don't need to carry my entire library of data with me (almost 1 tb). I have it all accessible on a NAS box with a PNP and itunes share. There's no need for it to be stored locally. And i recommend anyone who uses vast amoutns of media, to have a similar settup (backup, plus ability to use on any device in the house without worrying about ensuring everything is the same).
tis for US that the 64gb is around. if its not enough for you, that is why there's the 128gb model