I had a 250SE-L MM for 24 hours last month while my SportCross went in for a service.
It was a totally different driving experience to the old IS.
It felt huge inside, looked huge outside, was faster, smoother and more comfortable, than the old one.
I imagine its was probably closer to driving an LS than an old IS, although I haven't driven an LS.
And with all the new toys (6 x DVD changer, reversing camera and lights everywhere) its a great car.
Unfortunately, now with 2 tiny mouths to feed, it'll be a while before I own one!!!
Matt