NBN FTTN isn't available at mine until the end of August but even then I don't think I will change as Telstra has just sped up the ADSL2+ to around 17mbps down which is amazing. I use to be with Vodafone not long ago when they had turned on the 4G but it was only at most 3mbps down on full service 4G and limited service in a lot of areas. For instance Vodafone and Telstra don't work inside the shopping centres here but Optus works ok. Only thing is in other areas just driving in the CBD Optus could drop out for about 30 seconds then pick back up.
Will be hard to stick with Telstra, as NBN takes your copper and closes you down.
Aussie Broadband has a committment to building its own backhaul to the NBN POIs. But for now, they are using Optus in rural areas.