Latest idrive is pretty good and simple to use. I've had an E85 in the past and recently was given a brand new fully specced E89 sdrive 18i 8 speed auto for the week while my E92 had some work done.
I'm not a fan of autos but the 8 speed is pretty fancy, 18i lacked power though and it wasn't that quick and which made it hard to push the car to its limits and a bit dull and safe to drive.
Cabin is a little cramped but it's a nice place to be with the usual BMW quality. If I was to buy one I'd look at a 6 pot engine. The 2.0 turbo in the 18i was terrible on fuel only managing low 30's on the motorway, it also had some kind of fake sound generator which was funny at times as it made a lot of noise without really making any progress.
Front end takes some getting use to but no different to the E85, is very long and you sit quite far back so it's something to be wary of coming from a 350z. I clipped a rear wheel in my 350z a week after swapping my E85 for it, the 350z feels like a boat compared to the z4.