I know two people that worked as driver engineers. They both started off as contract employees, and were offered permanent positions after their jobs were done. One stayed with Apple for a time and later left to form a company that created the FPC (floating point calculator) for the early Macs and SunDial (the worlds slowest media player. He did well with both ventures. The other person became a contract software test engineer (He used the bomb app.) and was never offered a permanent positions again.
Both said that the work was just that, lots of work. There was a great deal of pressure and the money wasnt worth the effort, but the job opportunities were. Everybody at Apple doesnt speak about anything unless told, and the Icon Garden is as scary as it looks on QT. The fun corporate culture is dependent on who ever your supervisor is.
Oh, driver development often starts with out seeing or using the product in question. From what I was told, as I was told in non-specific terms, the engineers receive a set of specifications from both the manufacturer and Apple and they may start coding with the final product being present. I would guess that some sort of virtual device is created to test the interface until they receive the prototypes.
I have nothing but respect for people that create interfaces between hardware and software.