The new SLK350 is quite sporty and the 7-speed slushbox ain't bad if you swing that way. I wouldn't get one just because of the slushbox, but that's just me.
Why this choice and not the others? Because you said the magic word, "the missus". She already wanted automatic transmission so why bother with a Z4 or a Boxster? Sure, BMW and Porsche make slushboxes, but why waste it on a nice sports car. Might as well get one that's designed to take the slushbox yet still sporty.
Convertible hard top is always nice plus they got that weird AIRSCRAF option where the heated air comes out of the headrests to warm your necks.
Can you dig it?