I bought my first Smart(451) about a year ago. Initially it had some surprise show-stopping issues and I had some buyer's remorse for about a month while I figured out the issue and repaired it. Since then it has been a decent little car that's fun to drive, but there are some caveats I would consider before buying one...
I work on my own cars which drastically skews my repair costs.
If this is to be your only car, I wouldn't recommend a Smart. They appear to be nice reliable cars so don't misunderstand this as a slight on the car, but parts and support can be harder to find which makes it less desirable for an only car. With Smart leaving the North American markets, this will become the norm. Something more common, for which mechanics and parts abound, would be my suggestion for an only car.
The available space can be a real limitation. I have dogs, I occasionally buy lumber and other materials; I could fit all of the dogs or a surprising amount of lumber in my old car (Saturn SL1) but the Smart is a challenge to fit just one dog (they are big dogs). It's fine for commuter type loads; groceries, typical packages - some even pretty large, but space is greatly limited compared to most other cars on the market.
I have other cars so none of this is an issue for me; I drive the truck when I need to haul large heavy things, I drive the hybrid when I need to haul people or dogs, and when I'm popping off to work I drive the Smart. If it needs repairs and I can't get parts quickly, I just drive one of the other cars. I like to tinker and learn and it scratches that itch, too. It's a great car; I love it and enjoy driving it, but it has limitations and it isn't what I would consider a good choice for an only car given what one could acquire in a similar price range. Not trying to discourage, just trying to inform.