What external hard drives is everyone using with their air? I am planning on getting an Air, but the 128GB will simply not suffice, and I do not want to pay $300 for double the space on an SSD, and I do not want the weight of a Macbook Pro. So, I am looking to get an external hard drive for time machine and everything. I do not know of any major thunderbolt drives out yet, does anyone? Also, the air only seems to have USB 2.0.