Melbourne's Myki card seems to have been the most expensive to implement in Australia and the most complained about. Personally we don't have issues with the day to day use of our cards. We have about six Myki cards, one for me, one for R, one for Little Jo when she visits, all registered to our names, and three others, all found or discarded by someone at some point. When found one had a negative balance, one had a couple of dollars on it and one had $35 dollars on it. We save these for visitors who don't have or have forgotten their Myki card. I keep about a $10 balance on each card, enough for a day ticket. These were all unregistered cards. It is worth your while having a registered card if you are prone to losing things.
Public transport advocate Daniel Bowen recently visited Sydney and tried out their newish Opal card system. It is an interesting read. He seemed to think the card was good, but I would use stronger language about Sydney's fare system than he does. It is rubbish. It makes public transport expensive and the fare system is very complicated. My eyes glaze over when I try to understand it but to get the best from the system, understand it you must.
Canberra's My Way.
Perth's Smart Rider.
Lastly Tasmania's Green Card. This is the only private photo I have used from someone's blog and Tania writes a interesting piece about her introduction to Hobart's public transport buses and quite a bit about how things work in Hobart.