Pushlets have been used in many (commercial) applications and demos. Below are examples I know of. If you know of other products or your product is not featured here let me know.
www.geotracing.com - real-time GPS tracing on a Google Map
www.n8spel.nl - one of several GeoTracing applications
www.senseofthecity.nl - another GeoTracing application
www.qnadesign.com - see case study for www.marketnews.com
www.rabotreasuryweb.com - pushlet-based real-time market data
mis.sourceforge.net - a software toolkit for monitoring events
www.incito.com/ftseDemo.jsp - demo displaying real-time prices from the FTSE100