I've seen it work, first hand. My friend in Indiana has an iPhone and he has his email set to check every hour, but yahoo push is almost instant. Almost always right when I send him email. So, on the other hand, with mine, here in Metro Atlanta, sometimes I don't get the email till when the 15 minute check occurs...or sometimes its 7 or so minutes...totally always random, never instant though. I have tried deleting the account off my phone, restarting phone, and re-adding phone. I've even switched my phone at the apple store and exchanged it, same thing. And, I upgraded my account to Mail Plus... And, I've tried to add the prefix..nothing.