It's all about how relaxing the IS300h is to drive. Yes, I agree it's very quick in mid-range but will not match a high torque diesel. But we cannot compare the two as they are too different, so let’s leave it at that.
I love my car, have driven it for 5 years from new and it never ever felt stressed out even in situations where I would need to react quick in traffic. The electric traction gives good torque added to the engine power. It's flows great with traffic and is very frugal so what more does one want. These are the best cars in their class!
And would anyone agree that (off topic I know) the mileage a hybrid does is far less stressful on the engine then a regular petrol car. Mine has done 60k miles which is more likely to be 30k for the engine and brakes.