Well, if it ain't broke, as they say...

here's a page on the differences between Nchan and the Push Module: https://nchan.slact.net/upgrade . One important thing I forgot to add is that the Push Module suffered from memory fragmentation under high load, and with a fixed-size shared-memory chunk that could mean running out of usable shared memory for a long-running nginx process. If you're not experiencing that, and you don't need to scale up, or the new features don't appeal to you, don't upgrade -- certainly not yet.

Maybe in a month or two when nchan makes its way into the nginx-extras debian package (replacing the push module), then consider upgrading.