Hi there
I've owned only two Tiptronic cars in my life so far. One is an Audi S-Line A6 saloon and the other is the 996 Turbo I collected a couple of weeks ago. Before I bought the 911, I swore I would never own another car with a Tiptronic gearbox, because the Audi has to have the worst driver experience I've ever had. It changes at the wrong times, doesn't change down intuitively enough and is basically slow and tacky. Even in "manual" mode I hate it.
After looking at options when buying the 911, and after one or two sincere recommendations from folks with 996 TTs (Tiptronics), I decided that I would go for the Tiptronic rather than the manual. Collected the car with more than a little trepidation from the dealer and started out on the drive home. I was absolutely blown away by the responsivenesss of the 911 auto box. It changes crisply and almost instantly. When under braking, it changes down at, for me, exactly the right speeds and I'm able to use engine braking - unheard of in my Audi. When I bought the car I thought I'd probably be driving everywhere in manual mode but actually so far the box is just so good that I've tended to let it have its own way, with the occasional blip down one or two gears, depending on how emphatically I want to accelerate. Porsche have done a masterful job on the Tiptronic, at least on my car - it's magic.
Hope that helps.
Chris