We moved to in-house PM of our anaesthetic machines (GE Aisys) this year.
I think in general it has been a good move and certainly ups the skill and confidence levels of those involved however, as a workshop manager I am taken aback by the amount of resource it has taken to do this. It has meant a substantial rearrangement of other PV/PM schedules to clear most other work from the month when the anaesthetics "major" services are due.
Make sure you have the resource available before making the move to in-house!
Dave