push-in/push-out slots are really nice, but I believe they are unsafe to use unless you use synchronized (and slow) writing like e.g. Palm. For the N8x0 the operating system needs to know that you intend to remove the card before you actually do it, with enough time to do an 'unmount' on the card before you physically remove it. The 'unmount' includes flushing unwritten data to the card and waiting for it to settle.

With the current N8x0 design (SD slot cover, or magnetic detection) the operating system gets advance notice and can unmount the card before you remove it. (And you shouldn't be too quick.. particularly with the large size cards. Give it a few seconds after you uncover before you actually remove it.)