@Dan

I learnt today that some cards appear to be sold without the switch

With regard to the filesystem check: Make sure the device names are clear before unmounting and so. Check mount without any paramaters before you unmount. Oh, and just to avoid misunderstanding: I am talking about fsck for linux (be it Maemo or any decent Linux Distro.). On that same note I should wholeheartedly advise you to have a look at a nice LiveCD being made around gParted, the Gnome partitioning tool. You download an ISO, burn it and boot from it. After it started up, it operates as a mini system recovery OS. If it's not for now, I'm quite sure it will come in handy one day.

http://gparted.sourceforge.net/download.php

PS Rehearsing what?