I'm just catching up on this thread. Looks like a couple good options listed now for charger that does both the phone and spare battery at the same time. I noticed the Amazon like has an AC adapter, but the ebay link does not.
On the topic of charging 2 batteries, I often fly for 12 hours overseas. A single battery will not last. So being able to charge both at the same time is a big convenience. Swapping is a PITA, because normally I charge them over night (when I am not using the phone). Then if I'm always charging 1 battery over night.. how will I ever get 2 batteries charged up?.. Hmmm.. a charger that charges batteries separate from the phone.
And to answer the question about discharge rates. Lithium Ion batteries hold their charge a very long time, losing only about 10% of their charge over 30 days. So charging them up a couple days ahead of a trip has no significant impact on battery life.