Saw somewhere on the net, said drift wood was good for some fish, other than a good hiding spot, plecos like to chew on it? I will try and find out the address.
I had a loracarid that would munch away on driftwood. The wood will also slowly release small amounts of organic material (like tannins) which will give the water a nice color and decrease the pH slightly. Most characins love this blackwater effect.
ITs ok to buy. But it may lot sink right away. IT also might release some brown colour into the tank water. This is totaly safe, and as Ras said the fish will like it.