With WPA, MAC filters and SSID broadcast disabled you are just about as secure as you are going to be.
I have had people in my house, with their own laptops, unable to connect to my network.
No doubt some very clever hacker could - but why should he bother? You and I are not typical targets for extreme hacking - they tend to target businesses and institiutions where they know the information will be useful.
I have connected to my neighbour's wifi easily (by accident and without his knowledge) simply because he had taken no security precautions whatsoever.
As long as you have carried out these measures I should just stop worrying about it:
http://www.practicallynetworked.com/support/wi reless_secure.htm