I transferred money both in and out of my ING account. It shows up into ING the next day, but they do put a seven day hold on the money, you can't transfer it back out the same week.
When I transferred money OUT of ING, back to my checking account, I did it not for the next day but for about three days in advance, I knew I had to transfer the money by a certain day. Well, they transferred it on the day I asked and it showed up that day in my checking account. I would think that's unusual, but it should go in/out in a day or two, as long as you remember that weekend don't count. So a transfer done on Friday, would not start until Monday.