I stumbled across this article and thought I would share my experiences. Having signed up with Optus NBN from Telstra ADSL, I was quite annoyed initially. Having signed up to 50mbps, I was flatlining 25mbps during business hours, and 6-12mbps during peak times. After a couple of complaints, Optus let me out of their 24 month contract.
I signed up with MATE NBN on a 25mbps plan, getting consistent 17mbps. Although not 25mbps, I figured this was a better outcome as I knew I would not get the full 25mbps anyway - as someone above also stated. I then upgraded to 50mbps and noticed that my speedtest.net speeds had not increased, and neither had my line sync. I suspected they had not upgraded my line, but after a couple of calls they ensured me that I had.
NBN were then engaged by my RSP who eventually told me my line was within spec. I asked, 'in spec of 25mbps or 50mbps?'. The response I got was that I am 1274m (1100m line of sight) from the node and that 25mbps was the maximum speed that NBN believe is possible at this distance - at least for now (see below). What annoys me the most is that I have a node 400m line of sight away which would see me get much faster speeds. I know it requires laying a new cable however which if I really wanted to, I assume I could probably pay Telstra to move.
A friend who worked for Alcatel Lucent who supposedly provides the NBN equipment, mentioned that g.fast technology means that 1000mbps speeds on FTTN are possible - again distance would still impact your connection.
For me, receiving 13mbps on an ADSL2+ connection, I should have stuck with it considering I have gained 4mbps with NBN which was touted as being 'Super Fast', something it is definitely not living up to. I think NBN and RSPs have a lot to learn with the way that consumers are currently being informed. I do like the approach I read above with the 12/1 connections before committing to higher speeds, but this is a massive flaw.