I bought my '15 5-speed ES brand new in December of 2014. I now have 70,000 miles on it, and it has given me no trouble. All it has asked of me is gas, oil changes, brake pads, and tires. That's it.
Mirages are a bit noisy, not terribly fast, and don't handle particularly well. But they have a great set of standard features, get absurdly good mileage, have a great warranty, never break down, are intelligently designed, well-built, and are quite inexpensive. The pros definitely outweigh the cons.
I don't regret buying mine for a second. I have encouraged FIVE friends and coworkers to buy Mirages, and they are all as happy with them as I am.
Just be sure you are okay with a car that is pretty much the modern definition of an "econobox". Expect anything more from a Mirage and it might let you down.
All the feedback is great and I'm very aware of the car being an econobox and the engine which I can adjust to easily since the Smart is a small car with a three banger so the Mirage will feel larger by comparison and frankly I find the looks of the 17 pretty cool. I liked the way it bops around town and I love it.