It tastes delicious and has a fantastic aroma. It's quite complex. I'd put it somewhere between vanilla, marzipan and cinnamon. I've tried it with chocolate, almond, vanilla, fruit, cream, custard with good results. It also apparently goes well with fish (haven't tried it yet).

Yes, that part about his cooking experiment was rather ridiculous. It marries very well with vanilla and chocolate. By itself it has a bit of a sweet nutty flavor that is rather complex.

To be slighlty flippant, it's kind of the shitake (or msg) of desert, it enhances the rest of the flavors.

The article is correct that it tastes a lot like vanilla. Nothing special if you ask me, there's plenty of spices with more characteristic taste. Maybe if used by an exceptional chef will make a bigger difference, I don't know

I've heard that the actual fruit is very tasty but I've never seen or tried one

It's a delicious, sweet, nutty aroma that marries extremely well with chocolate. The Swiss chocolate manufacturer Villars makes a delicious "Praliné fève Tonka" that I can't recommend enough :)

Tonka bean tastes amazing. Hard to describe, it's vanilla-esque but doesn't taste like vanilla.