The battery performance of my 8 week old MacBook Pro Retina is disappointing but not as bad as others like Jake Needham are experiencing. I seem to get somewhere between 4 and 6 hours. The problem is not with the battery but with the power consumption.
About This Mac/More Info/System Report/Power will show you what's going on. I haven't had the personal energy to take this up at my local Apple store. But what the geniuses need to explain is something like this:
Just now, the full charge capacity of my battery is given as 8366 mA/h and the charge remaining is 4488mA/h. The power consumption (Amperage) is -2047mA. So I have 4488/2047 hours to go, i.e., about 2.5 hours and would have 8366/2047, i.e., just over 4 hours if the battery was fully charged - much less than the claimed 7 hours. 2047mA at 11 volts is over 22 watts and that is much more than Apple claim the power consumption for an idle MacBook Pro Retina should be. The power consumption seems to fluctuate unpredictably, but always on the high side.
If the geniuses insist that Coconut Battery says there is no problem then just click on the battery icon. For me, just now, it says that I have 55% and 2:30 remaining - but 55% of 7 hours is a lot more than 2 hours and 30 minutes.
See http://www.apple.com/environment/reports/docs/MacBookPro_Retina_Product_Environm ental_Report_June2012.pdf
for Apple's claims about the power consumption.