I've got a 7D with the LP-E6 battery that came with it, but would like to get some spares (along with a battery grip)
With my previous camera (450D) I used generic batteries (and generic grip) and had no issues with charge/usage, but apparently the LP-E6 batteries have a proprietary Canon chip in them, which means that there may be problems charging or using (in terms of battery metering) in a 5D or 7D body.
What are the specific problems? And are there any 3rd party batteries that have the Canon chip or a reverse-engineered chip to avoid these problems?