I see all the same things that you're talking about with the "sometimes" slight hesistation to select gear... and slight slow pickup "sometimes". The rev raises, do you mean around 2k-3k rpm? As that's torque converter lockup and that's the super smoothness.
The "sometimes" thing - I've tried one thing out. It's the i- in the gearbox, the intelligent part working out your style, and quickly too. If you are driving in super-slow traffic and then take-off, there's a slight delay while the ECU works out what's going on. And the same coming down the gears. Try this... cruise 20mph, and then give it a bit of power - feel the lag there, a bit too much. Now seconds later, cruise again at 20mph, and do the same.. It'll pick up this time.
Whack her in sports mode, and try some spirited driving - the box soon works out that you're not messing around. It's all Lexus smoothed ECU algorithms to provide that smooth pickup over surging I reckoned.
Sometimes makes the the VVTi-ed 3L engine feel more like a turbo in response, but the weird thing is the increase in torque as the revs go up to 5k-6k. Weird after the 400bhp 1JZ and the other (standard hp.torq) turbo'ed diesels that I drive.
oh, and one last thing. Black gearbox oil is BAD news in an auto-Toyota/Lexus. There is a gearbox oil filter, but even the service recommendation is the life of the box. Basically, it shouldn't be black. Or just red?