That's absolutely true, but even a strong passphrase can be "brute forced", it takes more time, granted. As has been stated earlier, the more layers of defence... the bigger the deterent.
Wireless is inherantly insecure, but like life (and flying) you have to weigh up the odds. Is little Johnny down the road going to try and hack into your bandwidth, with MAC ACL's, WEP/WPA and everything you can throw at it available, or is he going to use your next-door neighbours bandwidth, who doesn't have a clue about security ?