I looked at the Notes field, but stuck to custom fields, they work much more easily, and are easier to report on from SQL.
I record the following infor for all of my servers:
Application/Service
Category (i.e. Dev, Production or Contingency).
Comments
Approver Team
Maintenance Window
This way we can track services and easily identify who may be impacted if a VM or host fails, and makes life easier in creating change records that may impact the host.
An undocumented feature is that the Custome fields are always organised alphabetically not in the order you create them.