Well, if you want to give the lot of us some first impressions of your real-world battery life, I'll be happy to read them.
FWIW, got my rMB last week. Restored from a TM backup of my MBA so machines are almost identically configured (other than those differing due to hardware differences). Been traveling this week. Keep my brightness at about 75% in the office and 50% in the hotel. Under heavy use in the office, battery life looked to between 4-5 hours. In the office under normal use its 6-7 hours. In the hotel at night with light use its 9-10 hours.
All of these are based on a combination of predicted battery life by iStat Menu's and 2-4 hours use under each condition to verify that iStat looked like it was making an accurate prediction. E.g. under heavy use for two hours when iStat was predicting 4:30 at the beginning and 2:30 at the end seemed to indicate it was making an accurate prediction. I did not run down the battery to nothing as I was working and don't heavily use the machine for 4-5 hours in a row. Similarly I don't do moderate use for 6-7 hours in a row or light use for 9-10 hours in a row. YMMV because what I call heavy, or medium, or light use may not be the same as yours, and I did not do actual run down to 0 tests to ensure 100% accuracy (i relied on iStat predictions but did monitor for some period to ensure it looked like it was tracking accurately).
Based on one week of ad-hoc use, it looks like the rMB is getting better battery life than my MBA. It looks like the difference is smaller under heavy load and gets larger as load lightens. Battery health on my rMB is about 97% and on my MBA its around 99%.
