Is the power really still on? What happens if you connect it to the PC/MAC via USB? If power is off, I think sometimes you don't need to hold the button too long in fact I remember getting multiple vibration as you explained but instead of holding for too long I just held for couple seconds and it turned on.
Previously Owned Devices: Xoom, Samsung Galaxy 10.1, Samsung Galaxy 10.1 4G LTE VZW, Galaxy Note 10.1 32 GB, Transformer Infinity 32 GB
Currently Owning Devices: Samsung Ativ Smart PC 64GB, Ipad 2