My wife had this, which replaced her previous generation Z4, of which we have had 3 including an M.
This is the E89 version, no where near as sporty as the previous one but immensely more comfortable for longer journeys & is a nice place to be.
She went for the 3.0 as wanted 6 cylinders again. It’s brisk but never feels overly quick. She preferred her older car for how it drove, these ones are heavy with the metal roof.
Roof works well but does swallow up available boot space. I always had a fear the motors making the roof work would fail, and the price would be eye watering I imagine.
19” wheels look great on the car, and as all BMWs drives so much better with RFTs removed and a return to standard tyres.
If you can do the 35si go for it, on paper it’s got the pace of the Z4M so has a nice turn of pace when required. There is a great abs friendly U.K. owners club with loads of info and advice.
As mentioned above, ah missed the feeling of it being sporty, so we traded hers & my Z4M to get her into a Boxster. Gratuitous photo of exchange day!