I bought a 2004 dci 65 at the end of October and have already done 2k miles. I bought it to keep the miles off my 182. Currently averraging 62ish mpg. Can get 70 if driving very careful and not frequently going into low gears.
They do have issues, injectors being the main one. However, from what i have read up already, as long as the oil is changed regulary it will massively help it run as it should for a long time.
Tax is £30 a year compared to the 182's £285.