@syncro:
Selectable automatics and tiptronics run on the same principal. They're not only offered in porsches (I think Porsche's are soon going to be switching to VW's DSG setups), but they're offered in a lot of cars. They run on the same principal- the gearshaft regulates the engine through a torque converter, which is what gives the sluggish shift times, and overall slow pickup speed.
Yes I know the name tiptronic is exclusive to Porsche...