Well, i use Exetel at the moment but only really because they have good ADSL1 plans and that is all that is here in the exchange... I use or have used a few different places
Internode - great service and always good download speeds even in Tassie when i was on only one of the 2 ADSL2+ enabled exchanges. A bit more $$$ than some but worth it IMO if you can get the ADSL2+ service.
iiNet - OK but value has really dropped off with plans lately, seem to be targeting the mainstream rather than technical users nowadays, which probably changes the support nature somewhat. I had an old 512kbit connection ranging to a 20Mbit ADSL2+ connection at work and they were all quite good though.
Exetel - good from what i can tell, haven't had to call their support however, but they are cheap and offer good value. 60GB offpeak download on most plans which is from 2am to 12 noon, not that bad. They don't shape after hitting the limits on their plans (unless you ask them) and just charge $3 per GB. If i could get ADSL2+ with them they use the Optus network but i can't so i use ADSL1 at 8Mbps. They give free VOIP calls, SMS and offer a fax-to-email and email-to-fax service which i use pretty consistently.
Optus - had cable back in the day when that is what you needed to get decent broadband, way before any of these 3GB limits and stuff applied, it was possible to download upwards of 30GB per month for $75 a month or so. Unheard of in 2001. Nowadays they offer very poor value on their broadband plans along with long contracts and very expensive overuse charges.
Virgin - i use the 3G product for laptop "wireless warrior" use which works fine in the areas i use it in which is usually Sydney or Melbourne metro. 5GB a month for $34. I wouldn't use it as a home connection, but it does generally work 80% of the way down the trainline from Hazelbrook to Sydney which has to count for something.
Of course your mileage may vary wildly with any provider, my advice is fine a plan with enough downloads per month, enough speed (1.5Mbits is a bare minimum i reckon) and fits the budget, then make sure whatever it is doesn't have a ******* contract (longer than 6 months or requiring >$150 termination fee), and of course order online rather than talking to someone or being convinced by door to door salesmen. My mother and father in law have this absurdly crap broadband plan with massive overuse charges and a terrible contract and consistently have to ring them to fix things on their bill. I keep telling them that they could get 60-70GB on a ADSL2+ plan for the same price and get rid of their contract however it is like pulling teeth trying to explain it to them as they have been told "the cable service that XX offers is the fastest available"