For a macbook air 128GB (outsourcing libraries iphoto / itunes) and 3 PC
The wifi dual n is really faster (if one is not too far from the terminal) for data copies course for internet it does not matter.
Quite functional in a PC environment / Windows but does not work if the hard drive is NTFS (FAT32 or HFS), which can be a hassle if it is necessary to plug the USB directly to a PC for data-intensive .
(I have a small 100 GB partition to NTFS if needed)
By cons even HFS (Mac format) the data is visible on the PC via the router.
Time machine works perfectly, it just takes the partition on the HDD is big enough and HFS.
As against the access functionality to data via the internet is hype, it apparently works via the "Access to my mac (via iCloud)" that requires another mac !!
Otherwise easy to use and install, signed what apple ...