 This car has been pretty reliable with two exceptions:  First, at about 100,000 miles a hole melted in my exhaust manifold causing the car to make a lot of racket.  I ignored it until exhaust burned through an O2 sensor too (according to the dealership) and both had to be replaced.  Second, and most importantly, the transmission tends to overheat after an hour or so of driving at highway speed, and when that happens the car goes into a fail-safe mode where it will no longer accelerate quickly or drive above about 50 mph regardless of how fast the engine is running.  The only remedy for this seems to be to stop and let the transmission cool off for awhile.  Now it's starting to shudder too when it gets hot, but not sure yet what's causing that.  The implementation of the CVT transmission is the weakest part of the Altima design in my opinion, and there are a lot of reviews to back me up.  Also, the car thinks it's getting 22 MPG but if I divide mileage by gallons when I fill-up it is consistently closer to 20 combined, maybe 21-22 if I do mostly highway driving.