Without getting too far into the dirty details, GPush uses IMAP IDLE, which is the same system used for push GMail on Android and WebOS (Palm Pre) devices. Siegler says GPush works pretty well, even though "IMAP IDLE is generally thought to be not as good as actual push." GPush grabs emails within 30 seconds of their being sent, which isn't quite "NOW" push technology, but is an improvement over iPhone's manual fetch capabilities - though I kinda think if you really, really need your email RIGHT NOW you should be rocking a BlackBerry, anyway.
BTW, GPush has not yet been approved by Apple for inclusion in the App Store. And it may never be.
But that's not the point of this post. This is the point: iPhone OS's push notification system stinks. Apps like GPush - along with the bevy of push-enabled IM and twitter clients ready to gush on through the App Store - will only serve to highlight how iPhone OS was beyond state-of-the-art when it first hit the scene a few years ago but has lost a step in today's hyperconnected, cloud-based world of mobile computing. Android and WebOS have a huge leg up on iPhone when it comes to user-friendly ways of notifying you of new Emails, messages, calendar alerts and other events. I've written about it before - as has nearly every mobile tech journo/blogger on the planet - but Apple's "Stop everything and read this dialogue box now!" system just isn't very good.
Apple's notifications were fine when we were all still stunned into silence by the beauty of iPhone OS 1.x and 2.x and the otherworldly multitouch display it appeared on. Two years later, Palm Pre's display and OS look at least as good as iPhone's (if not better), and Android's gaining ground, as well. But both Android 1.5 and WebOS 1.0 have iPhone beat when it comes to keeping users aware of all manner of alerts without interrupting their current task and overall workflow. A glance at the image at the top of this post shows iPhone's clunky one-at-a-time "badge" system flanked by WebOS and Android's more modular systems that allow for multiple notifications that can be dealt with, ignored, or swiped off the screen at the user's discretion, all without interrupting whatever's going on in the foreground of the platform at a given moment. WebOS lets you flick individual notifications off the screen one-by-one while Anrdoid keeps them all tidied up in a notifications drawer that can be opened up and then tucked back into the status bar until later.
Push notifications on iPhone OS are a good thing for Apple and its user base, no doubt. But without having tried GPush myself - and that's a big but, I know - I can't help but imagine that a constant stream of badges alerting me to each new GMail message I receive might wind up being more annoying than helpful. iPhone 3.0's clunky means of alerting users won't be the platform's undoing - not by a long shot given the massive adoption of iPhones across the globe - but in the face of Android and WebOS' more elegant solutions, notifications are one area of iPhone OS that's suddenly screaming for a makeover.