I ordered the smart keyboard from ebay and I've been thinking about buying a smart cover as well (Apple OEM of course). I don't use a back case on any of my devices (knock on wood) since I prefer the feel of the aluminum.
The times I don't use the keyboard, I would have it attached to the smart cover. But if it's not that big a difference in terms of bulk / weight / inconvenience; I don't want to waste the extra money.
The times I don't use the keyboard, I would have it attached to the smart cover. But if it's not that big a difference in terms of bulk / weight / inconvenience; I don't want to waste the extra money.