You realise quickly whether you have the fob... the car won't unlock!
I just love the fact that the fob never leaves my pocket. With my hands full, I don't have to fumble for a remote to lock the car - even leaning your bum against the handle will do it!
BMW have shot themselves in the foot a bit with the new Five. It doesn't have a slot so it is keyless start as standard. To pay over £500 just to open the door without the fob is way over the top as starting without a key is over half the fun.
People seem to fall into two camps - the ones who don't have it - and half of them wish they did, and those that, given the choice, will have it every time.