"if the web2py models and raw GAE models are all different models there should be no problem. "
Actually the GAE models will stay the same because all the system is already tested and working. I decided to move to web2py when I saw it has auth and I implemented it for 30 minutes including jQuery Mobile layout. Which impressed me and I needed to learn more. So basically how I see it I will use only auth from web2py database all the rest would be GAE. "for my largest web2py project (starmakerstudios.com and the associated iphone app that talks to the DB)" It looks cool. Does the web2py handles the traffic in a stable way?