db upgrade does not fix all incorrect datetime values

[DrByte]

i think putting this into zc_install mysql_upgrade script would be an awesome idea.

Yes, that's the plan. I put it here first to get some testing feedback on databases beyond what I'm using myself.

2 of which were added fields (and would not be caught by the above sql statements)

Yup.

in addition, my test data for v155 also needed the following statement:

ALTER TABLE `products`
  CHANGE `products_date_added` `products_date_added` datetime NULL AFTER `products_virtual`;

i am not sure if this was missed in a previous update or if my testdata some how is out of of sync with what should be defined for a v155 dataset.

A fresh install doesn't use null for that field. Not sure why you're changing it to null (nor why you're not using the keyword 'default' as well).

Since v1.3.8 the schema for products_date_added has been:
products_date_added datetime NOT NULL default '0001-01-01 00:00:00',