I went without the Touchstone for my Pre for quite a long time, but once I got it, there's no going back.
I used to just throw it on the charger each night, but with the Touchstone, if I know I'm going to be in the room for a while anyway, I'll throw it on there and top off the battery.
Even without the fancy Exhibition stuff, I've gotten used to using it as a desk clock.
I'm actually planning on getting 2 of them-- one for each room that I expect to use it in. The convenience of being able to just pick up the tablet, knowing it's fully charged, walk into another room, use it, then drop it back down to charge again, without messing with wires, is totally worth it to me.
In short, you have better things to do with your life than messing with a USB adapter.