IMO - the tannins leaching out is actually good for the fish, but they can "o.d." on it (so I have been told, I have NO CLUE why/how) - like 3 years ago I had too much wood in a 10g tank and the fish in it died - I was told from the LFS it was because there was too much tannins leaking out and not enough water for it to "mix in" with (I wasn't doing water changes enough, I guess once a week wasn't enough since there was soooo much tannins) - I dont know if thats really why the fish died, but there wasnt anything wrong w/ the water perimeters and the fish wasnt sick...
What I do now: New driftwood gets tossed in the bathtub in the spare bathroom (or a bucket/rubber maid if you dont have a spare bathroom) and let it soak for a day, drain water, refill tub - rinse and repeat until the water isnt so orange - then boil and put it in the tank - works pretty well for me