I curently have TPG and it's been great so far, no problems at all and the speed is fantastic.
had Bigpond ADSL 2+ before this as it was the only option available through the local exchange and whilst it was very expensive, the service and speed was actuaclly pretty good. The few times I had problems I didn't have to pay for that month.
Try this website for all available ADSL2+ exchanges in your area. All you have to do is either enter your phone number or address and it will show the distance to the local exchange, service providers available and spare lines available.
http://www.adsl2exchanges.com.au
Cheers
Tim