I'm at a complete loss on this one.
I loved the Z4, to the point that it has become my lust for a 'fun' car. I'd give up the driving enjoyment of the Miata for the luxury in this kind of vehicle, and wouldn't even blink about the $10-15k more I'd be spending to get it.
...but at twice the price of a Miata, and gouging for packages, and $70k pre-tax without a backup camera?! FFS!
The roof in this is far more desirable than the one in the Z4, and the trunk looks equally awesome (it may be small, but it works for most of my needs - except skiing).
All said, if I move somewhere warm, I'll consider this, but RWD + low, low front just isn't conducive for a year-rounder 'round these parts.
Weather aside, the SLK's only redeeming feature to me is the roof. Otherwise, I like the Z4 packages way better. Shame the Z4 is slotted to be discontinued.