I am seeing the same thing. I had my new iPad on the charger using a wall outlet. The battery was decreasing while i was using it....
I'm also seeing that what used to charge my iPad 2 quickly on my 2010 MBP is now almost draining the battery. I was at 85%, plugged it in and it's been plugged in doing a restore for the past almost hour, and it's at 81%.
It's new, so it's going to need a few cycles to get it all figured out, so I'm not too worried. It'll get a full top-off tonight from the wall charger and I'm sure it'll be great tomorrow.
But yeah, I was surprised to see it drop 4% while it's been on and restoring. Course... the battery IS 70% larger