Hi NVRENUF

My 1kW system was installed Oct 2008. It cost about $2,200 all up -including upgrading the meter.
It generates about 1540kWh over a year. about what the installer estimated. would be higher without a bit of tree cover and facing north-west not north.
Of that it saves ~16 cents per kWh when the power is used, or from July 2010 the new buy-back tariff is ~45 cents per unit if sold back to Synergy.
If you are out all day and using very low power then most of the generated power is sold at 45c per kWh . If you are are home in daylight hours and running air con then the generated power saves only 16c per kWh.
1540 times 16 = $246 per year
1540 times 45 = $693 per year
Investing $2200 to save $246 per year would appeal to someone who needs to be kept out of the stock market.
Investing $2200 to save $693 per year is a fair business proposition.
So, it depends on how much of your generation is consumed or available for sale at the buy-back tariff.