The new open source OS that the Storm runs. It's by google. also, remember there is no MMS for the iPhone, which means no picture messages, so if you cannot live without them, that may be an issue. A work around is to just have people text them to your email and you'll get them in there, and to send them you need to email them to their phone. every phone number has an email address, I know ATT's is yournumber@txt.att.net and that will send a pic message to whoever I want that is on att, every carriers is different, and it's kinda a pain in the ass to set them up at first but if it's not a big deal to you, like it isn't to me, then it probably won't bother you. The phone has way to many positives that make that easy to over look.