Powerful targeting for iOS push notifications
blog.parse.com
blog.parse.com
Push notifications compete for user attention at the same level as incoming text messages and phone calls. Using them to announce a new version of your app is inappropriate, unless you think it'd be appropriate to call or text every user of your app to let them know about a new version.
Also, using push notifications in this way is arguably a violation of the App Store review guidelines, in particular:
"5.6 Apps cannot use Push Notifications to send advertising, promotions, or direct marketing of any kind"