The tireless tinkerers over at XDA have assembled a definitive guide to loading the Hero's custom-baked Android build onto G1s. It's fairly involved and a little risky, but hardly unfamiliar territory to HTC fans. [XDA, GetYourDroidOn—Thanks, Patrick!]
should be renamed, how to get a laggy OS on your g1 :) unless youre doing a build without the Rosie Home screen, its a gamble, some people say they have no issues with a class 6 microsd card, my coworker still had lag even with one, using JACHero builds too. homescreen and its nice widgets arent worth it to me, though I'm still using the hero rom without rosie because i like all the other OS differences, like camera, albums, facebook integrations, etc.