I traded my 2003 Boxster S for the 2007 Z4 3.0i. The Porsche had much more power and super handling, but I lay awake at nights worrying about a possible Intermediate Shaft Bearing failure (the dreaded IMS design fault) which was more a matter of when, not if, it would occur. It ran trouble-free for five months, and I loved it, but my wife thought that it was too loud and too fast (both are reasons for which I loved it, by the way.) A fruitless search for an Alpina B7 led me to look at M6 coupes, and I found a very pretty one, which is now in my garage, replacing the Z4. 507 HP never gets old. I do, however, as in three years I will be 80, and the authorities probably will not even allow me to own such a beast, never mind drive it enthusiastically.
David, in Brighton, Ontario, Canada