OK, my completely independant and unbiased view is go with Internode.
I've got Exetel at home, it is fantastic for what I do, d/l-ing, bit of surfing, but their tech support is non-existant. If you have problems you sort it out yourself.
My work has business ADSL through Netspace. It is fine. We never have speed issues despite litterally hundreds of people telling me we will.
A good friend is on aaNet 8mbit and is stoked. They are quite eager to please.
My old work was through Bigpond. They were expensive, unreliable and very hard to deal with. Never again, there are much much better options.
I've just signed out new Devonport office up with Internode. I've been dealing with them on teh phone the last week and they have absolutely FANTASTIC customer service! Their plans are reasonably priced also.
Basically, everyone, for one reason or another, is pulling out of Tasmania, hence shitty speeds with most providers. Telstra, OptusNet and Internode will remain. These 3 own their own hardware. Telstra has the best hardware (obviously), Optus uses Telsras old hardware so is always playing catch up, but Internode owns their own which is nearly as good as Telstra.
The fact Internode has invested in installing their own hardware in this state says they'll be here a while. They are cheaper than Telstra, more reliable than OptusNet. Can't go wrong.
By the way, you don't need anything more than 512/128. This is about 12 times faster than the dialup your using now, you'll love it. Also, steer clear of long contracts. 12 months is a maximum. Preferably 6-months. Plans are getting cheaper all the time so you don't want to be stuck paying huge amounts.
Something like the HOME-512-STARTER (
http://www.internode.on.net/adsl/pricing/home.php) would be my recommendation.