I bought my Smart car about 6 months ago. I love every part of it. When I first heard about them about 2 years ago, I decided that this is the car for me.
I am 6' and weigh 230lbs and have lots of room for me and my son who is 6' 4" and weighs 265lbs.
Maintenace is once every 10k miles (mine has been serviced once, cost me just $66 at a local shop, I did replace the air filter with one from K&N).
Most of my driving is by my self so only having 2 seats is perfect. No I can not carry a 4' x 8' sheet of plywood home or carry 6 people, but that is why I have a van as my other car.
I love the car on trips. I have made a 2500 mile round trip and a 600 mile round trip. No issue with either.
The sun roof is great, I just open it a little to let the rays in, and sometimes at night or when it rains I open it all the way.
Very easy to drive. I leave mine in the auto mode and let the car shift for me.
You can park it anywhere (the guy's are work scold me for wasting 1/2 a parking spot) and you can pull U turns on side streets.
The only thing that I would change is to have cruse control as a option or standard feature (going to add it one day).
This car is not for everyone. Do your research and test drive one before you buy. But for me its perfect and I love driving it every day.