I am curious as how the car drives with this steptronic in manual mode (I assume with the F1-style paddles on the wheel). IS it fast to shift up AND down like an F1 car/Fezza?

It does not shift as fast as a F1 car. I rode in a M5 which shifts harder and faster than the Z4 smg. Drive both and compare.

I guess smg and steptronic are different things. Somebody told that smg was used on older Z4 and was not good, and for this reason was replaced by steptronic.

Not sure which Z4s came with SMG but I'm guessing it was the same SMG I that was seen on a handful of BMW E46s. It was far inferior to the SMG II and SMG III so it was only in limited production. I've heard good things about the Steptronic on the Z4. I had it on my old 330 and it functioned just fine, kick down is cool.

I like my steptronic on the my Z4. Its really easy to use, however there is launch control or any way to launch the car like a manual or SMG. :(
Just test drive a car with one, and you will enjoy.

I was about to type that no automatic will be faster than an electronically controlled manual, but the possibilities in the future are endless with how companies like Lexus are improving the automatic. That said, no steptronic is not very fast. Why? Because it is a standard automatic. It isn't one of these fancy DSGs like in Volkswagon, and even if you get it with paddles it doesn't decrease shift time any. BMW's automatics are pretty sucky transmission too. They don't shift very smooth and tend to fail ~100,000 miles. Why? Because BMW doesnt' care about automatic drivers.

Ianbiz: To launch with your steptronic, put it in Sport mode and step on the gas all the way to kick down and you'll do just fine. Also DSC fully off as well.

I thought the Steptronic system is Tiptronic, licensed from Porsche. That seems highly thought of.

No tiptronic is what it's called on Porsches and BMW it is called steptronic

Maybe I'm thinking of Audi - I know someone licenses the system from Porsche for use in sports sedans.

I bought a 2.5i Z4 yesterday, however I don't have the car just yet. Have to wait till the 9th of November =(

Test drove that car, and really fell in love with the SMG system.
To be real hounest it feels a little rough shifting both at little pedal travel and WOT (come to think of it, maby the sport button had something to do with that haha)

You downshift with your thumb on either left or right side, and shift up at the back either left or right side.
I really like don't having to lift your hands of the steering wheel, and with cruizing you just put it on automatic and love it.

When standing still you don't have to leave your foot on the brake like on a normal automatic because it won't move.

Shifting is fairly quick, but like i said only test drove it once and fairly short.
Just treat yourself on a test drive you won't regret that!

(sorry for my English but i do have a good reason; i'm Dutch and you know how stupid we are ;) )

Mr X, be proud of your heritage! The Dutch are an amazing people, and you have a lot to be proud of!