Nicely done.

However, I think one drawback is that there is no way to re-execute a previously prepared query. Depending on the situation this can be a serious issue.

Update

Kanji asked me to elaborate...
The query method above always calls prepare. There doesn't seem to be any way to execute the same query with different parameters without prepare getting called. In DBI I can do:

$sth = $dbh->prepare(q(update foo set bar = ? where quux = ?));
$sth->execute('one', 'two');
$sth->execute('three', 'four');
...
[download]

Depending on the complexity of the query the prepare step can be very expensive...

Michael