Today I received my new nexus 7. I played with it for awhile and then turn it off to compare start up times with Galaxy Tab 2. I pressed power button and nothing happened. I tried different combinations and basically it will power on after 45 seconds holding power button or if it plugged in to charge. Battery is at 70%. I called Google tech support and the guy made it sound like it is a "feature" of the device. He was like if the device stays plugged in for too long, has low battery, or was turned off manually the device will take 30 seconds to power on. That just doesn't sound right.
I haven't really found any good tips apart sending it back.
PS: I haven't had any issues with Samsung Galaxy tab 2 for a month of owning it.