There is not a feature built in to Quality Center in either old or new versions that would handle this automatically. The Assign To, Detected By, etc. must remain as User ID fields because that is how Quality Center is built to reference the user to the user list. There is a commonly used customization that can be done by using the project Workflow script that would allow you to use the UserID of these fields and assign the full name to a separate user defined field. Below is an example of doing this for the defect's Assigned To field.

Sub Bug_FieldChange(FieldName)

'If the field that is changing is Assigned To.
If FieldName = ''BG_RESPONSIBLE'' Then

'Instantiate variables.
Dim UserID, FullName

'Get the new value of the Assigned To field.
UserID = Bug_Fields.Field(''BG_RESPONSIBLE'').Value

'Get the CustomizationUser Object for the user ID.
Set CustUser = TDConnection.Customization.Users.User(UserID)

'Get the FullName property for the user ID.
FullName = CustUser.FullName

'Kill the CustomizationUser Object.
Set CustUser = Nothing

'Set the User Defined Field value to the Full Name.
Bug_Fields.Field(''BG_USER_01'').Value = FullName

End If

End Sub

This is how we populate our Full Name field for Detected By. We have the code in in the Bug_New & Bug_FieldChange subs.

If Bug_Fields.Field(''BG_DETECTED_BY'').Value <> '''' Then
Bug_Fields.Field('''').Value = TDConnection.Customization.Users.User(Bug_Fields.Field(''BG_DETECTED_BY'').Value).FullName
Else
Bug_Fields.Field('''').Value = ''''
End if