Everything I've heard is that it's incredibly difficult to grow commercially. That said, there's a company in Half Moon Bay that's doing it. I can't say I've tried enough authentic Japanese wasabi to make a reasonable comparison with the locally grown version, but I can say that both are worlds better than the green goop you'll find in almost all Japanese restaurants. I know people who can't handle the spice level of "normal" wasabi but have no problem with the real stuff - there's more flavor there than just "spicy", although it still carries a fair amount of heat. The grated version also has both texture and aromatics that you won't get in wasabi from a tube.