I ran into more issues than most because the particular AP I have at home doesn't work well with the macbook air I was trying to backup and resulted in a lot of disconnects. So it was a bit of a stress test but the issue is real and well documented. You can find instructions all over the web on how to fsck sparsebundles to try and get back your backups[1].
This is particularly annoying because Time Machine is supposed to be a user friendly version of versioned backups like you can do with rsync+hardlinks. I have a script to do that for me on my personal linux machine and would love to be able to deploy TimeMachine+AFP for the rest of the family. Unfortunately apple decided it really needed to have hard-linked directories for just this case and so decided that the way to do that over the network was to have a single binary blob with a HFS image on the server instead of the proper files in the filesystem (filesystems don't usually support hard linked directories, HFS was hacked to do it). That way you not only lose direct access to the individual files on the server you also lose the whole backups when there's disk corruption...
I should probably have a look again to see if iSCSI is a viable solution to this.
[1] http://www.garth.org/archives/2011,08,27,169,fix-time-machin...
Note that this is completely unreliable. Time Machine isn't built to work over the network. The network support is badly hacked together and will destroy your backups on network faults. They basically treat the network volume as a block device that gets corrupted when the connection fails. Using it over wifi makes this painfully obvious.