I have a nice padded carrying case for my tripod, so I always check it and have had no problems. Some airports (like Atlanta) make you pick it up in an "oversize" luggage area, so you might have a moment of concern at the carousel until you figure that out.
If you are worried about it being damaged, the safest (and probably cheapest) shipping container I have heard of is home-made from pvc pipe. Put a cemented cap on one end and a threaded one on the other, and it's practically bulletproof. I've never felt the need to resort to this.
Another tip I learned for large checked items such as tripods, light stands, etc., is to buy a rolling case for golf clubs. They are not very expensive and hold a lot of large items.