Very nice to see that article here in Onlamp and thanks also for the good critic on my Pear DB Tut. Just only few corrections in the example you give:
1) $dsn = array(
'phptype' => 'mysql',
'hostspec' => 'localhost',
'database' => 'test_db',
'username' => 'test_user',
'password' => 'test_password'
This is supported, but the "string" format is shortest and more recomended. So:
$dsn = 'mysql://test_user:test_pw@localhost/test_db';
2) simpleQuery is not in use right now, to launch the query simply use $dbh->query().