How fast is the SSD going to be in the Air compared to the 4200RPM drive. How much of a difference will it make in booting, loading apps, and other tasks? Also, would an SSD considerably extend the battery life? Is it likely that Apple Service would add do a replacement for a buyer of a conventional drive with an SSD at a later date? Surely the prices of these drives will plummet soon now that they are going to be produced in greater numbers.