To exclude results that have empty properties, you can easily use Where-Object. For example, when you run Get-Hotfix, and you only want to see hotfixes that have a date for InstalledOn, here is the solution:
Likewise, to get only network adapters from WMI that actually have an IP address, try this:
Note that in PowerShell 2.0 and below, you need to use the full syntax like this:
Where-Object will exclude any results that have either one of the following in the property you selected: a null value, an empty string, or the number 0. This is because all of these will convert to $false when converted into a Boolean value.