Any Z3 or Z4 owners?

[Perfectlap]

I'm considering a Z3 or Z4 for purchase (and eventual export).
Not really for my personal use but I'll be handling the purchase and any modding that will be done and then shipping the car to an overseas friend who I can't convince to go the Porsche route due cost of maintenance.
I do however have the Z4 coupe high on my list.
Any first hand experience? Track/Autocross? Would you have considered
yourself an enthusiast the same way you are a Boxster enthusiast?
I had a brief run in the both and I was happy with the feel of the car, more so the z4 of course.
There seem to be some good deals to be had.
How does the ownership experience from a repair/maintenance/gas consumption compare to the Boxster?