In a real sense, the fact of the long time between test drive and deposit and configuration. That leaves a lot more time between decision and a buy no buy decision.
I've had a few fairly major back and forths on getting the smart. I could see the roads just shake the heck out of a smart. (still a hmm... a matter of perception) I could see snow tires being maybe an issue. (Got over that- not a problem). Distance from a dealer (a really good one, btw) is a question.
If I walked into the XYZ dealer and ordered a xp134rxi sportster in January, I'd have the car now and have to live with my concerns. With this system of hurry up and wait we have plenty of times to get all worked up over important or not so important issues. Its still up to you to go or no go on the smart.