I have. Even ridden in the back like cargo, all that space is really good for. What has caused you to consider one, exactly? And a brand new one for that matter?
They're alright for exclusively city life if you don't mind how silly they look, how mediocre their mileage is for such an anemic and tiny engine (my Yamaha V-Star 1100 had a bigger engine) in such a tiny car, and the lack of useful space.
If you really want one, see of you can find someone looking to dump their used one and go from there. If your current car is good enough, keep saving what you would've been paying monthly until you can afford to buy a decent small car with cash. There are lots of great small cars out there these days. I wouldn't count the Smart line among them, except for very specific and rare circumstances.
If you simply must look at brand new small economy cars, check out the Ford Focus and Mazda 3. The Scion tC really isn't bad either.
Eric (the Deacon remix)
The follies which a man regrets the most in his life are those which he didn't commit when he had the opportunity. - Helen Rowland, A Guide to Men, 1922