Coming to the 335xi coupe from a '00 328Ci, the 335xi is a more grown-up and far more powerful car. The engine lives up to its reputation and then some. Amazing low end torque - really does feel like a V8. This makes the 335xi a very different animal from the traditional BMW inline-6 car, and while quicker, it feels somewhat less sporting. With the old inline-6s (and presumably the new 328) you really had to spool up the engine. Now, you don't have to push it and if you do you're soon over the speed limit. Great fit and finish. The xi drive is fantastic in poor conditions, although the xi suspension is softer than in my old E46 (more body roll). All-in-all, very happy with it.
Engine: Amazing power and sounds great. Xi drive: Makes the car a far more dependable commuter in poor weather. iDrive: Maybe there are other systems that are easier to use, but the integrated nav, iPod controller, phone is fantastic. Dynamic re-routing around traffic disruptions is great.
iDrive: Improve searching nav for nearby businesses (have to choose a category before searching now) Xi suspension: More body roll than I would like. Car doesn't feel as sorted as an E46 in corners. While it may be the AWD, a tighter suspension would help. Run-flats: Get rid of them.