Here's another data point.
14 months since delivery 3/31/11
Coastal Orange County, CA
I've charged about 26 times per month, almost always overnight with some public charging each month and two QCs. Home charging has been to 100% about 98% of the time. Car is mostly driven smoothly, with early average energy economy on the dash of 3.8 mi/kWh, now averaging 4.0 mi/kWh.
I have not lost a capacity bar. Nissan dealer battery report at 12 months, April 11, was 5 stars on all parameters at 11,600 miles.
80% charge overnight from 163 Gids on 5/29/12: 225 Gids, voltage 387.5, ambient temp at time of reading appx 65 F, overnight low temp 57 F.
100% charge overnight from 77 Gids on 5/30/12: 274 Gids, voltage 394, ambient temp at time of reading appx 64 F, overnight low temps range 59 to 61 F. Charge was done with timer override, beginning about 12:40 am, ending at 5:05 am, with car still plugged in until 8:30 am.
(Temp readings are from iPhone weather app, not recorded temps in garage. Garage is un-insulated flat grey rock roof.)
My car was routinely getting 281 Gid readings after 100% charge, with occasional drops to as low as 278 Gid, but my records show outliers for 100% charges in January of 275, 267 and 271, February's lowest was 278 Gid, March had one reading of 269 Gid after a 100% charge from only 28 Gid, April only one low reading of 275 Gid. May started out with 280 and 281, but started dropping on May 6 with 272 Gid after a 100% charge from 103 Gid. I haven't seen anything above 279 Gid since May 4, with low readings of 272, 274, 274, 275, 272, 272, 276, 273, 269, 275, 270, and today 274.
One other point: I started seeing readings not higher than 278 after May 12, a day when I put 95 miles on the car, having driven to Cerritos and then charged mid-day to be able to do some evening driving. Again, 280 and 281 Gids were reliably routine with my car, the last such reading being May 4.