I bought my Toyota Yaris (or Vitz as it is known in Japan) as a second-hand Japanese import.
The performance of the car is pretty decent for a 1.0 litre (manual) engine. It accelerates well in the low gears - 1st and 2nd. However, if you don't push the engine hard in 1st and 2nd gear, it won't accelerate quickly in 3rd, 4th and 5th. You may think this is obvious, but I find that the acceleration is horrible if you don't at least push the engine slightly hard in the low gears. Moreover, I find that I give the car €10 of petrol every 2 days - this is quite a lot considering I don't do too much long distance driving - but since you have to push hard in low gears, you end up using a lot of fuel. In short, if you push the engine hard in low gears, you will be very happy with the performance of the engine. Otherwise, you will find it underpowered.
The engine, like all Toyotas, is very reliable.
What I find very annoying is the performance of the car with the air conditioner on. I know that every car with a small engine will have a reduction in power with the A/C on, but I was surprised at what a bad effect the A/C has on this 1.0 litre engine. With the A/C on, even if you push the gears hard, you feel a very noticeable lag from when you press the gas pedal down to when the car takes a sudden boost in acceleration. This feels almost like a turbo lag (without the turbo-powered acceleration of course).
I am very unimpressed with the handling of the car. At speeds above 70km/h you feel like you have to pay a huge amount of attention not to lose control - you have to hold the steering wheel very firmly when going around bends at speeds over 70km/h. The car however remains stable in a straight line at 130km/h and does not vibrate like my old Peugeot 106.
The ride of the car is pretty horrible. My old Peugeot 106 and my girlfriends Fiat Punto mark 2 had better rides. I live in Malta, where the roads are full of pot holes, and in the mark I Yaris you feel every single bump on the road.
What I hate in this car is that it feels so light. When going down a long steep hill at over 70km/h on a windy day, you feel like the wind is going to blow the car off-course. Moreover, if a car in an adjacent lane coming in the opposite direction passes by me at a high speed, the wind it creates makes my car take a small sudden sway, and you almost fear that you are going to lose control. Its like what you feel when you are standing at a train station near the railway and a train passes by you - you feel like the wind is you to move you or something. This is what happens to the Yaris.
Driving at speeds of over 70km/h with the back window/s open creates a horrible very loud and disturbing wind noise inside the car.
The position of the clutch pedal makes it uncomfortable for you to leave your foot resting gently on it, as you have to leave it at an awkward upright angle. This is not so with the brake pedal, as your foot can rest gently on it comfortably.
What I find annoying is that the first gear is very short, and if you push it too hard you'll find that the engine will protest by shuddering and grunting, causing you to quickly change to second. Second gear is short but at least it allows you to reach about 70km/s before acting up. I never experience the shudder and grunting if I pushed the car too hard in my Peugeot 106.
The extras which came with the car are very good. The car has ABS, double airbags, A/C, integrates CD/Radio and pretty decent standard speakers. I wish the car had ESP though, as the car slipped and I almost lost control when I was going down hill at speed and changed lane and then quickly changed lane back to where I was again.
Other than the thing which I mentioned which really irk me in this car, nothing has gone wrong with it. Everything runs fine - however I've only owned this car for 7 months.