I hear you. I went through the same thing with a client that came to me with a 1.6 install. After spending the better part of a weekend trying to upgrade and migrate and get everything to work, I tossed it and rebuilt the site in 1.5 from scratch, which actually took half the time of the upgrade, and now everything is working great and I've already moved on to the next phase of the project.
After that, I made the decision to stick with 1.5. My arsenal of 1.5 extensions can accomplish more than the new base features of 1.7 anyway and I can get the job done in half the time. Just my experience.
The difficult we do immediately, the impossible takes a little longer.