It's a microcosm of all bicycle related public discourse with the usual disgusting, violent bike haters having a field day on the media's (channel 7, from memory) un-moderated comments. Melbourne BUG has received a lot of very positive feedback, people posting videos of bikes using the new roundabout etc.
It appears most bikes are using the green painted bike lane rather than going with the cars, and are appreciating the improved safety and priority through the roundabout. Of course it's not a problem if someone on a bike wants to go the slightly more direct route following the cars, the main point is to provide the conditions that encourage a wider range of people to ride, but it's important that the new roundabouts are seen as successful. As these will be Victoria's (Australia's?) first protected roundabouts, a lot hangs out their success.
One interesting issue to watch will be safety. This type of rab was pioneered in NL of course, and there are two types of design there, one in which bikes have right of way, and some where bikes don't. The UK/dutch blogger David Hembrow points to stats which show the type with no bike right of way are safer for bikes. Our new roundabouts are giving bikes right of way, and given it's a new design we might expect car drivers to make mistakes. So that will be something to watch. I should say I'm all in favour of bikes having right of way :)