Personally, I'm not a huge fan of the Z. I think the style will start to look dated in the coming years. I did drive the 6 speed and I felt that the engine, while powerful, seemed a bit unrefined. I didn't like the transmission much either. Don't even get me started on the interior.
They are cool cars though, don't get me wrong. I just wouldn't buy one. Lots of people like them and if you do, I'd say get one.