The difference between the S-extreme reels and the other Z models are as follows:
New gears (smoother, stronger)
New bearings (more corrosion resistant)
New drag (carbontex style material - no more stickiness on startup)
Bearing at the bottom of the handle stem replaced with bushing.
I've been lucky enough to play with one of the early production models for a while now and have had a lot of fun with it. The reels should be in store within the next few days. I'll post a few pics shortly
Cheers
Duncan