Passing through security at US airport with a brand new laptop

Unfortunately, it will depend on the screeners at your lane that day.

The point of removing the laptop and/or checkpoint friendly bags is to separate the laptop from other clutter in the bag. Original packaging is easy for the machine to see through so if the screener is satisfied, they may let it pass.

For the lowest probability of the original packaging being opened, put it in checked baggage.

The official page has this to say:

Starting Aug. 16, 2008 TSA began to allow laptops to remain in bags meeting "checkpoint friendly" guidelines.

I copied the criterias and numbered them:

1. Your laptop bag has a designated laptop-only section that you can lay flat on the X-ray belt
2. There are no metal snaps, zippers or buckles inside, underneath or on-top of the laptop-only section
3. There are no pockets on the inside or outside of the laptop-only section
4. There is nothing in the laptop compartment other than the laptop
5. You have completely unfolded your bag so that there is nothing above or below the laptop-only section, allowing the bag to lie flat on the X-ray belt

Only 2. is surely OK the rest is at least debatable.

Especially 5. can be problematic: if your box is like

with the charger on top of the laptop, that's a violation of the rules. It also can look like this:

which can possibly be sold as adhering these rules if the foamed part of the box is a "designated laptop-only section".

Ultimately, however:

If a Transportation Security Officer finds that the bag does not present a clear and distinct image of the laptop separate from the rest of the bag, the laptop must be screened separately.

So it's possible if the box gives them a nice look they will let it pass. However, at the end of the day:

Given TSA's use of random screening protocols, TSA reserves the right to re-screen any bag or laptop regardless of the design of the bag.

You can never know. This is the TSA.

You'll definitely have to take it out since they're scanning it through but I think you can send it in the checked in baggage without opening it.

I've done it, but before the era of laptops-out. Had they wanted it opened I would have had no problem with that--I was intending to open it anyway. I had told my machine to synchronize a bunch of stuff onto the laptop and woke up to find a major electronic failure of some kind. I spent as much time as I could burning relevant stuff to CDs, then stopped by the electronics store on the way to the airport, grabbed the most likely looking prospect and the memory to upgrade it and headed on to the airport. Once we were at the gate I unpacked the laptop and put it in my laptop bag.