I've had NBN installed for nearly a year now and no problems with installer or performance.

Prior to NBN I was on ADSL2, my ADSL cost was $75 per month and I got 250gb of data at 5mb/s download and 2mb/s upload speed.
In comparison with the NBN with the same provider I am paying $75 per month and I get 500gb of data with the speeds of 50mb/s down and 20mb/s up. I don't know why you would not go NBN if you have access to it.

Installation was good process for me, 3 contractors turned up and they asked me where they want the external box mounted. They were happy to help out and install it down the side of the house (an extra 20m of cable - no additional cost). I was up and running in a couple hours.