As someone who was doing web development at that time (since '96 actually), oddpost did have an impact on perception of JS and what was possible among developers. Yahoo buying them was kind of a big deal at the time, and every developer I knew who was involved in web stuff had seen it or at least heard about it.
The biggest drawback at the time was that it was window/IE only, and when gmail was released, google made an effort to be cross-platform.
IMO, Google's 'big win' wasn't so much showing what JS could do, but that complex JS could be done cross-browser and cross-platform.