lol, if tegra is only as powerful as the A4 i'd be worried... the A4 is literally EXACTLY THE SAME as the stuff in the 3GS, just clocked higher!
also, nvidia: WRONG! smart phones are fast enough now! the focus is on EFFICIENCY and battery life more than performance! and your latest graphics cards are hardly a shining enforcement of your capabilities in that department...
still, on the performance side, its a powerful combination, and I would expect that first Tegra2 android device coming out at the end of the year to SERIOUSLY kick the ass of the iphone 4g!