All the way back in 2009, I reviewed the Notifications app for ReadWriteWeb and wondered if it was going to be the best push notifications service for the iPhone yet. At that time, it had more features than Boxcar, which was still in its infancy. It was also one of the first apps of its kind to use PubSubHubbub to speed up notifications of updated news feeds. over time, Boxcar ended up trumping Notifications in terms of features and the difference in speed became negligible. Now, however, Notifications is is back as Push 4.0 for both the iPhone and iPad ($0.99 - iTunes link) and while its feature set hasn't changed much from the early days (Twitter, email, RSS), the developer Fabien Penso has worked hard on making it the fastest push app out there - and, I'm happy to say, he succeeded.