I heard that the flash storage in the MacBook Air is faster than SSD since it doesn't need to go through a SATA interface. How much faster is the MacBook Air's hard-drive compared to a traditional SSD?
It's still a SATA interface, just miniaturized, hence it's name mSATA. There is a great picture at the following link that shows just how tiny an mSATA drive is compared to a regular 2.5" laptop hard drive. Intel's SSD 310: G2 Performance in an mSATA Form Factor
Directly comparing the new MacBook Air against the older model on SSD performance alone, the new MacBook Air is much faster. This is from personal experience and from benchmarks found on various sites posted below:
Old MacBook Air SSD: http://forums.macrumors.com/attachment.php?attachmentid=100432&d=1201904233
Can't comment on SSD comparisons with regards SSD drives found in other MacBook models.