If you've never had fresh wasabi, you have no idea what you're missing. It's fiery, but it has a rich and complex flavor under the quickly dissipating burst of heat.
There's every chance that even though you've been eating Japanese food for years you've never had real wasabi in the first place. The little piles of green paste you get in a sushi restaurant are probably dried horseradish root, chinese mustard and a touch of green food coloring. Wasabi it ain't.
If you're really lucky, you might get real wasabi paste or a small portion of fresh chopped wasabi rhizome, stalks and leaves. We got fresh chopped wasabi at Sushi Totoro Sunday night. It isn't cheap, so they don't give it to just anybody. To tell you the truth, I'm not sure if this is something they're going to stock regularly, or if it was just something special.
If you're incredibly lucky, you will get a solid bit of wasabi rhizome and a sharkskin grater. Rarely does a restaurant carry and give out whole wasabi rhizomes, and if they do it's usually a large line-item on the bill.