Nice work, google maps is very cool. Have you already seen the google maps run info on American Whitewater? Here is a link to the AW site for Upper Mish on the Poudre (click on the map tab on the top of the page):
American Whitewater - NWRI - Cache La Poudre 6. Steven's Gulch Access to Mishawaka Inn
They already have the putin and takeout points in google maps and have the option to display the USGS Topo Maps which I think is very helpful when planning runs. They do not show the river line data but that is represented in the USGS Topo layer or the standard google map layer.
I like what you've done but think it would be better to spend the effort improving the AW google maps site than creating something entirely new. I think the following improvements to the AW maps would be nice:
-show the river line data for the run (this is easy to do by converting the GIS data to xml).
-show alternate putins, campgrounds, major river features, etc as points as you do on your google map
-Have a link to display that data the data in google earth
The whitewater community benefits tremendously by having more members join AW and more visits to their site might mean more boaters join AW. Just look at the awesome work they did negotiating over access to Cheeseman over the past few years. Ive been working in the GIS mapping field for a number of years and would be willing to help out, PM me...