a little bit (a friend's old job). there was a 5 year non-compete clause in there, but having researched it the accepted norm is 6 months, maybe a year in exceptional circumstances. we're planning to bust the 5 years and see them in court if they want to fight it - we took legal advice and they'll lose.
main thing we discovered is that they can not enforce a non-compete clause simply to "stifle competition" - there must be a valid reason e.g. an employee leaving and poaching all the company's customers.