Hi
i have had my 250 se-l auto for 18 months and i agree with a lot of what has been said so far. i love the smoothness of the engine and gearbox combo, and it is the most comfortable car i have ever had, until you flick the power switch, and start using the paddles and drive it like you stole it, then it is a totally different car and throws itself into the corners with vigour and no wallowing or squirming lol.
i do have to say that the earlier models (the ones 2005 to about 2009, which are the ones you would be able to pick up for around 12k) do rattle horrendously. I was shocked at how much mine started rattling and it does annoy me intensely, but the only problem i have had with it is the rattling so overall i count myself lucky. the few later models that i have had as courtesy cars have been a lot better and didn't seem to have the rattle problems that mine does.
all in all, i would still recommend the IS. i don't struggle to carry 4 or 5 adults in mine, with luggage, and the economy is nt that bad - i get around 29 to 30mpg around town and anywhere from 34 to 40mpg if i include motorway mileage. if you can put up with the rattling then i am sure you will be as happy with yours as i have been so far with mine. try to make sure you get an se-l with multimedia and you will be getting thousands of pounds worth of kit standard that you won't get in the german rivals.
regards