Love the lines of the IS, the rear light clusters set off a new style on after-market parts so hey the car was way ahead of it's time... the only thing I would change is the ugly orange indicator in the headlights go for HID's and get a proper body-kit on it just to get the body lower to the ground and add some extra muscle ( and off-course a sensible lower ride, read coilovers)
if that's all done the car is up to date and very very nice! ( still lacks the DLR lights but that can be sorted, after-market has loads of options)