I haven't played one yet.
Here's a video (thanks, Carlos!) with Jim Cheek doing a side-by-side comparison with a Yanigasawa A901. Jim sounds terrific on both horns, but you can hear the difference. The Yanigasawa has a crisper attack, and a richer sound, with more highs in the spectrum.
I listened to some of the video clips on the company website when my wife was in the next room. Her comment was that when played by a really good player, this horn is like a $10 bottle of Vino Nobile from Trader Joe's. I'll interpret: Not bad, especially considering the price, but it will never be a $50 bottle.
Judging from the video clips on the company website, the mouthpiece makes a large difference in the tone (of course).
But really, why shouldn't someone be able to make a decent plastic sax, theoretically, anyway? We've had plastic clarinets for a long time, and they can be quite good, depending on the manufacturer. And of course, there was the Grafton plastic sax, in the 1950s. Charlie Parker played one at the legendary Massey Hall concert in 1953, and sounded just like he did on any other alto (allowing, that is, for the very low-fidelity recording techniques of the period).
Vibratosax makes several alto models, differing mainly in the composition of the polycarbonate. You can read more about this on the company website. Only altos so far.
Here's a "Repairman's Overview." Matt Stohrer lists some possible issues with the design and materials:
It sounds to me as though all-metal keywork might have been a better idea. In general, I'd worry about long-term durability.
Piyapat Thanyakij's talking point about the "waterproof" qualities of this horn reminds me of this classic video from Hermeto Pascoal. If you are looking to recreate this performance, a waterproof sax might be perfect for you:
If you are an "early adopter" sort of person and just have to check out this horn, you can click here to buy one.