I figured out a good solution this weekend, at least it's the best I can come up with until an actual GPX viewer for iPod touch comes out.
You can use Safari to load the html output from GSAK (or whatever program you use to convert GPX -> HTML) and browse it that way. I get around the Mobile Safari limitation of not being able to load local html files by installing apache (in Installer.app under Network) and putting the html files from GSAK into the doc root for apache. Then I just setup a Mobile Safari bookmark to point to http://127.0.0.1 to browse the files