Haven't had any major problems with the car so far. The most serious was when the CD player wouldn't eject a CD but spun it at high speed inside the player.
I used to drive a Peugeot 406 with a petrol engine. When the mileage was too high, I decided to sell it and buy a different car - not French and a diesel for a change. I test-drove Ford Mondeo, Audi A4, VW Bora, Mazda 6, Honda Accord (2-liter petrol) but wasn't happy with any of them. Then I gave a Peugeot 407 a try and made my decision to get one.
The car looks great - well, I like it. Interior is modern, clean and functional. Buttons and controls seemed a bit chaotic first, but one can get used to them quite easily.
All seats are comfortable. There is enough space for a tall person like me on the front seats. However, there isn't so much space on back seats. I even struggled to place the car seat to the back - I had to shift the front passenger's seat so much to the front that it is not comfortable anymore to sit there for more than 3-4 hours.
The 407 has a small boot for the size of the car. In fact, my wife's Renault Megane (1998) has a bigger boot. Comparing to Peugeot 406, the new 407 is smaller inside and has a smaller boot.
The 2-litre turbo-diesel is a great engine. Very powerful, without the annoying acceleration lag that Mazda's turbo-diesels suffer from. I expected it to be a little less "thirsty" though. According to the on-board computer, the average diesel consumption is 44 MPG (6.4 litres per 100 km) with 33 MPH average speed (53km per hour). I know other diesels (Honda Accord, BMW 3-series, VW Passat TDI PS that my mates drive) achieve lower consumption providing equivalent (or better) performance. But hey - they are much more expensive.
The only thing I miss in SE trim is the cruise control. You can get an aftermarket cruise control fitted (even with 407's original stick control) but that costs more than £500 and I think it's not worth that money.
I don't regret buying the 407 - I'm only sorry I couldn't find a good deal on an estate, since with the new baby coming soon the car will be too small, especially for long journeys from England to Slovakia that we do at least once a year.
UPDATE:
I got the original cruise control fitted in a Peugeot garage in Slovakia for about £40. Works great! The fuel consumption has improved to nearly 60 MPG on long journeys with it!
I got a roof-box so the size of the boot is not an issue any more.
A CD gets stuck in the stereo sometimes and makes an unpleasant noise when I try to eject it. Quite annoying.
Other than that, everything is brilliant. I love the car!