I'm less concerned about erase as I almost always do format the card in camera anyway
The main concern is about erasing the card, before you can check thoroughly, if all images have been imported correctly. I never erase the card, before I have made a backup of the card and opened each of the images that I want to keep at least once on Aperture.
but I've been surprisued twice now with OS X saying I removed the card improperly after I told Aperture to eject it and waited plenty long enough.
Can you eject the card from the Finder?