Completely understand the hesitation in upgrading. It can definitely be a pain. We did it about a year ago. It certainly wasn't fun, but was necessary (for us). Joomla 1.5 is a solid system.. but there are no more security releases being planned for it, so please stay vigilant.
If you weren't aware of it, there's a patch for 1.5.26 to fix a major security issue:
joomlacode.org/gf/project/joomla/tracker...racker_item_id=31626
I'd highly recommend installing that if you haven't already.
Anyways, best of luck, and thank you very much for the review. We definitely appreciate it!
Thanks, and best of luck,
Alex