Ok, I've had the updated ECU for SMG transmission in my Z4 for a week now. I've logged about 300 miles and I am very, VERY happy. The problems with it hesitating between 2nd and 1st gear are gone. Just in general, shifting has been quicker and smoother both in upshifting and down shifting. Shifting from R to 1st and back is alot faster. A couple of other people who have gotten the upgrade are reporting the same and the problem with it shifting from 2nd to N are gone.
If you have an SMG in your Z4 and would like to see if you have the old ECU, just remove it and see if it has the blue dot sticker on the unit. If it doesn't, call your service dept and make an appointment. You'll be glad you did.
This link will take you to a web page that shows how to remove the ECU. SMG ECU Removal Instructions
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2003 Titanium Silver Z4 Roadster 3.0i SMG
Z means Zooooooooooooom