Many years ago I drove a Renault that had a "credit card" sized and shaped key, and a push button... it was cool but i inserted the credit card into a slot anyways, so, turning the card (or the key), would not be much of a trouble... but, i had to push the button... so, in my opinion it was ridiculous... So, i am not a big fan of a push button...

i just recently got an e90 for my wife, that has a factory push button. It also has that convenience entry/start option... Now, this is totally a different story - with key in the pocket (or in the purse, for her), the push button makes perfect sense.

So, in my personal opinion, the push button makes sense only if coupled with a convenience start option...