Right. Vauxhall have produced Auto's with this feature for donkeys years.
I have had several Omega's now, and not a single one (all 3.0) has made the slightest difference when in Sports Mode. In the normal Economy mode, when you plant your foot through the Firewall, it will redline in every gear and accelerate as fast as the engine will allow. I understand that if you engage Sports Mode and drive normally, it will not change up as quickly as usual, and will lock out overdrive (unless you hit an indicated 131MPH (as I found out tonight (on a private road))), but why have sports mode on if you aren't giving it the beans?
Other Vauxhalls I have driven with the Auto Box (smaller engined varieties), the Sports Mode has made a small difference, hanging onto the gears for slightly longer, but that's all.
So, Omega Compadre's, does that little 'S' button really help with performance in the Omega? :-/