I live near MK and go there for the theatre which is excellent and shopping when dh makes me (I hate shopping). It has good leisure facilities but I believe the schools in some parts are not great. Good rail limk to Euston which is why we live here although we are a couple of stops further towards London.
The traditional villages outside it can be really lovely. The shopping is useful and there are some nice parks. MK itself <shudder> If you have dcs, choose area carefully, some of the schools are dire.