To be a PM for an matrix Organization, as stated by @rv347 is difficult due to more responsibility given to you, more time needed to complete tasks and overall need to love working. So to be a PM of Matrix structure may have more turn over of employees due to the stress one acquires. To address this issue a PM if want they want to should work for an Project or Functional based organization. The PM will have people working under her or him which will alleviate the demand of responsibility. Since they have more power it suggestive when it comes time to hiring a PM they need to have reference whom can be spoken to ask about their qualities in terms of personality, how they work with people can they resolve issues in a patient manner.