I had one on my Sentra SE-R Spec-V for the 4 years I had it without a problem. Sounds awesome. It gave it a little more pep, too.
A Nismo product installed by Nissan (this would depend on the jackass-ness of the dealer you work with) will not void the warranty on the rest of the car. So, if you roast a MAF sensor, they should still cover it under warranty. Just realize that it has its own, shorter, warranty than the rest of the car. 12,000 miles and a year, maybe? So, if a part of the intake breaks after that, you're paying for it.
Those terms also change with whether it is R-Tune (race) or S-Tune (street) NISMO part, but I can't remember that difference. Maybe someone else can chime in.