Basil, I purchased an '05 MCS last year and it seems to be a very well-engineered car. It's very fast and there are few, if any production cars in it's class that can outhandle it on a curvy road.
The "S" model has a very stiff suspension. Folks who are not used to sports cars may not like it. The non-S model's suspension is not as stiff and it also gets slightly better fuel mileage. Depending on the driver's needs, I'd strongly suggest the S version. Resale value is better and it's simply a blast to drive. The non-S is pretty sluggish.
If you really want some fun, opt for the "John Cooper Works" package. For about $6,000, you get 210 HP at the front wheels (the S has about 170, plenty for most folks).
In about 7,000 miles of mostly highway driving, my MCS averages 30.5 MPG by the trip computer. There hasn't been a squeak, rattle or one single problem with the car.
It's a great car for the money, and the resale value is outstanding. If your wife likes small cars, go for it!
Let me know if you have further questions, I'll be glad to help.