I have learned my lessons and backup the sd card to prevent frequent reinstalling.
But how do I make sure i have a file system in good health when I decide to start an image backup. I use Open Source Tripwire to check integrity of some important files on my lovely raspbian box. (I use the standard configuration and only out commented/changed the rules about /proc).
That way I learn to use the Tripwire program as well. This will be usefull when I connect my Raspberry Pi webserver to the wild
In any case I feel much more secure about my image backups.