I'm wanting to replace my existing late 2008 unibody Mac Book with the new Air. Resigned to 256 Gig Model (still debating 11" or 13") but going I5. Currently I'm just using around or under 256 gigs on existing Macbook. Saw the idea of using a 64 Gig SD card for additional storage which I like the idea of. What could be stored nicely on the SD card? Could you put itunes Library on there or maybe even Imovie Library if not too large? What about backing up if you go with external storage (either SD card, or external Hard Drive). What would be the best solution to back up the Air along with the external solution? Thanks!