Slow and unpredictable? As, in Normal mode, the transmission has only one 'gear' the 'box is always predictable. The system brings up the engine revs as required and in line with what one experiences with a traditional auto box in kickdown.
Put the car into Sport (or Sport+) mode and instantly one has clearly defined "gears". Place the transmission into 'S' mode and one can have instant, 'PlayStation' like gear changes at the touch of a shift paddle. Change down in preparation for an overtake is just as one would experience from a manual gearbox.
IMHO the E-CVT transmission is the best 'automatic' style transmission I've ever experienced. Add in the relatively simple mechanics one has a very reliable, flexible and responsive transmission.