I think a couple of bad assumptions are being made here:
1) That we will only find Level 2 charging at our homes and
2) That we will only plug in at home overnight.
Both are not true. Private companies are already putting up level 2 charging stations. There will probably be more of these than the Level 3. Plus many of us in the Seattle Electric Vehicle Association (SEVA) make our own home charging stations available to each other as a shortcut to a broad charging infrastructure. Also, we have created a simple adapter that can be used to turn any simple dryer plug or stove outlet into a J1772 Level 2, 6.6kW capable supply station.
Because of this, having the ability to charge at a 6.6 kW rate would be a big advantage. Go visit grandma, plug into her dryer outlet in the garage and restore lost range at better than 25 miles per hour. Why wouldn't we want that capability?
Add to this, the information supplied by Nissan on the Level 3 charging option. Apparently it inputs so much power that the heat build up is actually harmful to the batteries. Nissan recommends you only use Level 3 charging once per day at most. So better to think of 6.6kW Level 2 charging as the highest safe charging level for the Leaf battery.
I would really like to see Nissan step forward and answer this question. Why such a dinky charger and when can we get a bigger one? Also, and most important, if we buy a Leaf in 2011, will we be able to upgrade to a larger charger later on. If that's not going to be a possibility, then leasing looks like a better option than buying.