I'm lukewarm on the whole pushbutton start thing. None of the three Toyota hybrids I've had (two Prii and a Camry hybrid) had the remote start feature, which is good, since that's the only feature I firmly DON'T want anything to do with.
As for the rest, again, lukewarm. The one part I really do like is that the system makes it
virtually impossible to lock the keys inside the car. The sensors are good enough that they just won't lock the doors if the fob is inside the car.
I said "virtually" since I got curious one time, started thinking (often very dangerous. . . ), and did some experimenting. Here's what you do if you REALLY want to lock your keys in a Prius: Fold the rear seat down. Get in the car and lock the doors. Turn the car OFF if it's not already so. Climb through/over the front seats into the back seat/under hatch area. Use the manual emergency hatch release to open the hatch from the inside. Climb out the back, and close hatch. Presto, you've just locked your keys in the car. See, we humans are still smarter than our cars!
UPDATE: I did this trick on the old Prius years ago, and it worked "like a charm" (assuming locking the keys in the car is somehow "charming"). It's a quiet day, so I decided to go try it on the new Prius. And guess what --
it doesn't work!!! I climbed out the hatch, shut it, and the car let out a loud, long beeeeep, and then unlocked all the doors. I guess I'd have to disconnect the 12v battery to "succeed" in this experiment -- something I'm not going to do. Oh well... Not feeling so smart now.