According to the acceleration data we got of the ride on out visit there last august then the I would say about 75 km/h.
The launch force is about 1g and the duration is roughly 2.1 seconds. It's very similar to Rita and Desert Race, but with a top hat at the beginning and much smaller, so the lower speed is really expected.
1 g = 9.8 m/s^2
9,8 m/s^2 * 2.1 s = 20.6 m/s
20.6 m/s * 3.6 (value for converting from m/s to km/h) = 74 km/h
The ride though is excellent, one of the best accelerators I have ridden, mainly because it doesn't induce massive headaches as it's larger siblings does.
Here is the complete graph of the forces on Senzafiato:
red = acceleration, blue = vertical, green = lateral