Google is offering the ability to sync contacts and Google Calender entries instantly as well. All of this functionality has been present in Google's iPhone software for some time -- just not with Push. Setting it up easy: If you already use Google Sync, it's just a matter of toggling the setting. Google noted that the always-on nature of Push email would result in heavier power drain -- something to consider if you treasure your battery life.
Although Apple is still against the idea of making the iPhone a multitasking device (for a variety of reasons), they have allowed outside applications to including Push functionality. As software development on the iPhone matures, more programs support some form of Push, which makes an Internet-connected phone all the more interesting to tote around. Hopefully development like this continues to improve on several fronts.