A colleague of mine has just turned up to work today in a Smart Roadster. It's a 54 plate with 48k miles, full history, and he got it for £3500. I just filled the tank in the B10V8 and it almost cost me that much.

The Smart is rear-wheel-drive, handles like a lotus elise, weighs around half as much as a 3 series, drinks less juice than sick toddler, and can be taxed and insured for buttons. It has an electric folding roof with removable 'targa' side bars, paddle shift semi-automatic gearbox, and you can even get a Brabus version with 25% more power and still average 50mpg.
Some of the reviews bemoan the lack of sophistication and dash quality. It's hardly an alternative to the Alpina Roadster but that's not the point. I'm looking at it as a modern interpretation of the Fiat X1/9. I reckon my colleague will get 50,000 miles of fun commuting over 5 years out of this car and the total cost (including depn) will be just over £2k per annum, or circa 20p per mile. That puts it on a par with my motorbike - but you can drive the Smart without a helmet and talk to the passenger. Not only that, it will keep you dry in the rain and top up your tan in the sunshine.
If most of your mileage is spent commuting or driving congested A-roads, what's not to like?