Eneloop batteries do not self discharge like standard NiMH batteries. After storing two for a week, they lost only 1% of their charge compared to 10-15% for standard NiMH. The Eneloop batteries only store about 2000 mAh, 20% less than the 2500 mAh Energizers batteries. In my digital camera this was about an hour less run time. I have put several AA and AAA into use in my universal remote control and wireless mouse to see how long they last. Standard NiMHs last around 2 months before I have to recharge them in these devices. I am expecting the Eneloop will last 6-12 months.
There isn't much of a price premium for the Eneloop batteries so I am probably going to start buying these cells exclusively. They store plenty of power and will cut down the amount of time I need spend charging batteries. I still have to test how they hold up with higher charge rates.
For my existing standard NiMH cells I am going to continue to store them in the freezer to lessen their self discharge rate. The batteries only loose about 5% of their charge per week, but have to be brought to room temperature before use to ensure they have a long life. Here is a chart that shows how temperature affects the self discharge rate of standard NiMH batteries.