Fun factor is off the charts. I bought this car for my wife, who commutes to a part-time job. We already have two other vehicles, so practicality wasn't a concern. She decided she wanted a small convertible and after reading a lot of reviews, this is what we chose. We've had it four months now with no issues. I understand maintenance can be costly on these, but we haven't had a single issue. It gets decent mileage (it would get great mileage but it's so much fun to step on the gas in this thing), it's comfortable, and it is the most fun car I've ever driven, hands down. It has surprising room for the driver and passenger, but the backseat is only good for two mid-size passengers and even then, only for short distances.
The controls are not intuitive; it is too cramped; the design has a lot of uncomfortable flaws-- for example, I have to move the seat forward so far to be able to push the clutch far enough down, that I cannot unfold the side visor because my seat back is in the way. I don't like having to sit so close to the wheel and never had to do this before, though I am short. Reverse is right next to 1st-- Several people, including myself, have shifted into reverse by mistake when trying to shift into 1st quickly. It is no where near as good on gas as my previous car which was a Prius, even though it is so much smaller and cramped.
I went in pretty much knowning I wanted a mini cooper. I was able to find a nice 2004 with what I wanted. One of the main things is I had to get a manual transmission as I heard the CVTs from that year are notorious for going out early. I'm able to get around ~350 miles per tank if I'm doing a lot of highway driving. One thing I like is the on board computer will calculate your average MPG as you drive. Straight, flat highway I can get about 36 mpg. Overall my mix of driving leaves me at ~30 mpg through the life of a tank. It is a mini cooper so the trunk space is pretty limited. I'm 6 ft 1 though and driving it is still plenty comfortable. It has pretty tight suspension and you feel every bump in the road. Whether or not that is a pro or con is open to interpretation. Shortly after I got it I had some issues with the power steering going in & out. They weren't able to reproduce the problem when I brought it in but has been holding up since so I'll just keep my fingers crossed on that one.