Get the count of AD groups a user is a member of
There are many ways to count things in PowerShell. Measure-Object is one, but my preferred choice is the count method:
(Get-ADUser <username> -Properties MemberOf).MemberOf.count
Personally, I would be more interested in the recursive (nested) group memberships of the user. This provides a more complete picture of what they have access to. To get all nested groups a user is a member of, you could use the constructed attribute tokenGroups (as explained here):
Get-ADUser -SearchScope Base -SearchBase (Get-ADUser <username>).DistinguishedName -LDAPFilter '(objectClass=user)' -Properties tokenGroups | Select-Object -ExpandProperty tokenGroups | Select-Object -ExpandProperty Value | %{(Get-ADGroup $_).Name} | Sort-Object