Meh....not interested at all. Since many of my DCC engines run with sound already, I really enjoy the directional quality of it. Running at shows with my fellow train-crazy Gregg Cudworth, who has tunnels on his section of the portable layout, I REALLY like the sound of my engines coming out of the tunnels, and even a slight (real) doppler effect as the engines go by at a grade crossing with warning whistle blasts.
Frankly, for the cost of the Kato/Soundtraxx Sound Box, a Digitrax Zephyr Plus and a Digitrax 8 bit sound decoder (which comes with a speaker) would be maybe even a bit less cost-wise after discounting...and, you'd be able to run more than one engine at the same time at different speeds and directions on the same track.
I am not impressed.