This is a comparison, not an advertisement!
All of the steps that you've taken to this point are the pain points that Zend Core for IBM is trying to address:
The major technical difference is that the PHP database extension is the ibm_db2 driver, instead of PDO.
Apart from ease of use, you also get a free support incident from Zend -- and support for Cloudscape is available from IBM.
But it's lots more fun doing it yourself :)