I'm on the Telstra $79 cap and I find it great for what I need.
You get $550 per month including GST, but at a rate of 70 cents a minute, plus the connection etc. I make around 300 calls a month of between 2-8 minutes on average with some longer and some shorter. Combined with a home line I get a discount so it costs me $68. I think it works out to around 20-22 minutes talk per day for free. It covers SMS and all services such as 12456 call connect etc, but it only includes $100 worth of calls to non-Telstra phones so you need to be a little careful.