There's a new review of the NAH in USA Today this weekend.

Basiacally they said it's much sportier/faster that the competition (TCH) but was not as smooth as the others - more vibrations.

An interesting note was that the Nissan spokesman was quoted that the vibrations could be "tuned out" if the customer desired it. I would assume that would mean less performance but they didn't say that.

"If your big issue is drivetrain smoothness, Altima's not for you. The gasoline engine shakes and shimmies when it automatically starts and begins augmenting the electric motor's power. Most hybrids mask the shakes much better than Altima, although the Camry hybrid is no champ in that department.
Perry says Altima's stiffer chassis tuning transfers the engine shudders more readily. 'We can tune that out if people tell us they don't like it,' he says."