So I bought a Steplight Power Meter to monitor the power being drawn from the wall. This result is only with 1 x 7970 card. Haven't bought additional 3 yet, Monday...

I worked out from our last Energy Australia bill that I pay an average rate of 27 cents / kWh.

Data -
Total Time Running:   1728mins
Total Watts Used:       5227W
Average Cost / kWh:   $0.27
Average Hash Rate:    520MHs

Calculator Estimates - from http://blockchained.com/profit/index.php?hashrate=520&cost=1&electricity=0.27&power=181&months=1.0000&decline=0.63&blockcoins=0
At the current Difficulty of 4367876, currently paying 25BTC / Block and current BTC value is at AUD$43.43, the calculator estimate I should get back (excludes capital cost):

After 1 month: AUD$40.94 (or approx. 1BTC)
After 1 week:   AUD$10      (approx. 0.25BTC)

Results so far -
After only 6 days and nights of mining with, several hours of down time (server upgrades and my own mucking around), lets say a week for simplicity, I have:

Pending Payout (confirmed):    0.22547869 BTC (which if sold at current price is AUD$9.79)

According to my calculations it will cost me around $35/month for electricity. Which means I'll probably break even on running cost... I can live with that!!!

Anyone care to check my numbers??

Cheers,
QG