Some hangups I had in this process:

1. Took a few read-throughs to catch that the default uc_order.tpl.php file had to be in my theme folder as well my custom templates.

2. Didn't see an obvious reference to HOW to flush the theme cache. I used the Devel module but apparently just doing a full flush on the performance page does it too.

3. This was the killer for me. Before I could get it to sending anything aside from the default templates (despite what the conditional actions said) I had to open each conditional action that had to do with emailing and click "Save predicate." That kicked things into gear.

As a side note, I'm sure there are logical reasons, but building a custom module just to add some email templates is pretty annoying.