depends on the car to write a car off it needs to be 60/70% of the value of the car, now factory in a 10k car thats 6k worth of repairs, now parts play a major factor in this, if the repairs have been done well its fine, but remeber you will eventually want to sell the car, and may loose out then.
i have bought/sold ex write offs in the past, and its not a bad thing, we get alot of car in that get written off due to the cost of new pannels were we allowed to use second hand or non gen then they would be saved, i myself bought a mk4 golf that was cat 'c' this had simply been stripped for the leather recaros, now to put it back to factory spec would mean full interior and wiring loom and airbag ecu, for me i rejoined the wired and fitted new seats job done,
so there not all lemons, just look at the quality of wok, paint finish gaps, make sure it drives stright, look for uneven tyre ware and still dameged chassi legs etc