In reply to R8JimBob88: First, this is only a fall back option when something has gone wrong. I've been climbing for many years and have only ever done this once and that was on a hybrid slate route where the runouts meant that climbing it bolt-to-bolt wasn't an appealing option.
Second, from my expereince mentioned above it does work perfectly as advertised and is the best way to bail, provided you are low enough.
Third, you are very right to be concerned. The LAST thing you should use is a sling. If you are going to do it you should only ever use a prussik loop (normally 125cm x 5mm cord) which is less susceptible to damage, only costs about 70 pence to replace and should probably be on your harness in any case.
HTH