After i transfer i always burn the original footage to dvd straight away,that way if anything goes wrong with pc or hard-drive,i've still got original footage on disc which i can edit from..
My cam hard-drive can hold 21hours on low quality or 7 hours on high quality,so i can get everything i want copied to pc and edited before i erase cam drive.If i need to film something else before i've finished editing first project then i've probably still got enough space on cam drive to film second project aswell.
I've never had any problems with my hard-drive cam,either with filming or transfering footage.
FYI it's a Sony DCR-SR90e.