When you want to configure your user import you will most likely want to filter out certain type of account; those that are disabled, system accounts, etc.
The following two filter will let you do this:
1) Import all user accounts except those that are disabled
2) Import all users except thos belonging to a certain group:
Combining these to (after first included all system account into the SystemUsers group) should give you only those users that should have user profiles.