I ordered the battery-only one a few months ago. The whole AC adapter thing is overblown...this thing doesn't use much juice--if you have to change the batteries more than twice a year, I'd be shocked.
That said, there's a significant issue with this swing where the bar that supports the seat isn't level. It tilts downward 10-15 degrees. Not a big deal if you're doing the side-to-side swinging, but if you turn the seat 90 degrees, the child is tilted and doesn't stay comfortable for long.
Have received zero help from the manufacturer, so it's a bit of a bummer. As a result, we hardly use it anymore as he prefers the back-and-forth motion to the side-to-side.
So--if you get this, check if the seat post is level/parallel with the ground. If not, I'd contact Woot.