We've had TT Earthwood teak and walnut on our deck for a year now, and not many issues. I have seen mold, but it's in an area that gets dirty from debris washing off the roof during rainy periods.
Installed in September, 2008, I first saw the mold in the spring. It wasn't serious...just a small amount of surface mold on a few boards located under the roofline. My husband couldn't even see it with the elaborate "grain" pattern the teak has. I used a hose and light scrub brush to remove it, which took a little elbow grease, and I didn't see it again until now. I will wash it again before winter, maybe use Corte Clean this time, and see how it goes in the spring.
I should add that I have an upper and lower deck of identical materials. The lower is protected by an Undercover System, so it doesn't get wet...just damp from misty rains. Not much mold on lower deck at all.
So, in my experience, I would still recommend TT. The Earthwood is beautiful, especially with hidden fasteners. They're definitely worth the extra $. It is not entirely maintenance free, it does have to be cleaned a couple times a year, but so does everything.
I hope my mold issues don't become a nightmare like some of these other stories tell. I will not go down the road of using sealers, stains, etc. I don't even want to use chemicals because they always seem to break down the deck in the long run. Good luck to you.