NBN state is less than stellar, a vast majority of suburbs have no NBN at all, and a very small minority have actual fibre to the premise. Unmetered plans are becoming more common but are only "affordable" ($60-70 a month) at the lowest speed offering (12mbit). If you want unmetered at 25 or 100mbit, you're looking at 80 or 100 respectively, and that's looking at TPG and iiNet.
FWIW (and I know this is a single data point), but my experience with NBN has been positive.
It's also Fibre to the Node (FTTN) which is often maligned in internet/tech circles for being a poor technology choice. I'd prefer FttP, but it's not an option and I'll take what I can get.
I'm now getting close to my plan's speed (50/20), but you're right about the increased cost. It's roughly 45% more. But the speed from the old ADSL2 plan is probably 4-5 times faster.
The only complaint I would have is that speeds during peak are pretty off the advertised plan speed. They fall to around 18-20mbs down at night.
