Word of advice: Don't double up your floor mats! Remove your carpeted mats and just use the rubber ones.
Nissan issued a warning awhile back about the dangers of doubling up floor mats... there are issues with the accelerator getting stuck or limiting travel of both the accelerator and brake pedal. This can cause sudden unintended acceleration, reduced braking and acceleration.
This has become such a problem that Transport Canada recently issued a warning:
http://www.tc.gc.ca/eng/roadsa...1.htm
As for the Nissan all weather floor mats, they are OK. I had some in my Altima and found the edges weren't tall enough to keep water from spilling out. The Weathertech Floor Liners are much better as they have very tall sides... I use mine year round.