As for regular users, it is still a bad system that refuses to be fixed!
It's always worked perfectly well for myself, much better than buying those silly Metcards all the time. I got my first card in December 2010 and have had three since, due to myself losing them. All four cards have worked perfectly fine. I honestly think the whole myki-bashing phase is just another bandwagon for people to jump aboard at present, as Today Tonight and A Current Affair haven't given the media worshiping masses anything else to be irrationally angry about. Myki is here, Metcard is gone, get over it.
As for my views on Short Term Tickets? I see no point in having a dedicated short term ticket. However, as has been suggested by others in this thread, why not have an return service available to visitors, where you return the card at the end of your stay and get whatever money is left on the card as a refund, minus a small fee to cover card damage etc.