would you trust your Linux installation if Lenovo had installed it?
Just receiving the new sputnik, oh hell no, the Ubuntu install was so broken. The benefit of shipping it with Linux is at least they made a decent attempt to work with Linux. Why an attempt? See first sputnik laptop.
No but I would at least have more confidence in the driver support for the hardware included.
In this day and age, I don't see how any (profit-based) company would provide a clean and trustworthy install.
If Microsoft forced them to.
Regardless of whether you trust the pre-installed software, it would assure that the hardware and firmware are compatible with Linux. Whether they rely on proprietary drivers is another question though.