That's a lot to answer lol....
Ok... Fuel consumption is pants but as Noby said is pretty much the same weirdly! Looking at 300-400 miles a tank or 25-30MPG.
I have a 200 manual Sport and the acceleration is acceptable but nothing special. I personally think it needs more power. The 300 feels a lot quicker.
Common probs, sticking brake callipers, (very common) dodgy cd player, they all seem to pack up lol.
Engine is bulletproof in all models and if maintained correctly will go past 200k and beyond easily :)
I think they must have been branded differently in oz as we don't have sport luxury model. We had the S, SE and Sport. S being the basic model with not a lot extras. No heated leather seats, no electric seats etc. the SE was fully loaded as was the Sport. The sport had a few extra touches such as a two tone steering wheel, alloy pedals, lower suspension and LSD to name a few.
Don't know how much you should pay as prices over there differ from here.
If I was looking to buy an IS again I'd get a 300 :)