Ok... the counter view....
Salveage repairs happen for 3 reasons:
1. The car is so seriously damaged it can't be repaired.
2. Its been stolen and recovered (sometimes with crash damage)
3. The cost of a replacement car plus repairs is higher than the cost of writing it off.

If it was written off for number 3 then it may actually have very little damage to it. If 1 then don't touch it. If 2 then bear in mind you have no idea how its been driven until it was recovered (but then you don't know that anyway!)....

Apply the usual methods of checking but just do so even more rigourously...
Also if possible find out what was wrong (photos showing damage are very useful!) and what was replaced and whether genuine parts were used.

Basically just take care....