Formatted storage and actual storage will always differ. Expect the new Air to have around 118 ish GB or less after OS X has been installed
Of course, I know that!
But in the case of the 64Gb SSD, everyone would have expected a 59 or 60 Gb formatted storage capacity. Yet, all those who got one got actually quite a bit less (there are several thread on the topic). Some people actually wondered whether the disk was not less than 64Gb unformatted, whether the whole space was actually recognized or whether Apple was doing something smart (or not) with 4Gb.
If the 128 SSD has 118 Gb storage space after formatting, I will be very happy; if it has less than 110 Gb, I will be much less so.