And the 3 cylinder is a gem of an engine. On paper, it makes 134 hp and 162 lb.ft of torque. In the real world, it feels exactly like how those figures suggest it should feel: When you roll onto the gas, you get a surge of low-end torque to keep up your speed, but you have to rev it out to get any meaningful acceleration (admittedly, there were three people in the car when I test drove it). This power delivery is interesting, because it means you still have to rev it out (slow car fast), but it has enough torque that it never feels slow in everyday driving. The best thing, though, is the exhaust note. It has the same deep growl you get from a V6, which isn't surprising since a V6 is just two inline-3's glued together. While I haven't driven the 2.0T Cooper S, I imagine the 4-cylinder sounds fairly similar to the 2.0T in my B7 Audi A4. And the 1.5T 3-cylinder is by far the better sounding engine. At the end of the day, it's a very eager and energetic engine with way more charm than you would expect from an entry-level premium hatchback.
And here's a 0-60 run someone did so you get a taste of what the 3-cylinder sounds like: