Depends on how much of a risk-taker you are, or how handy you might have a couple thousand laying around should something major happen after the factory warranty.

In this case, you aren't gaining a whole lot, since the drivetrain warranty runs for 60K/5yrs. On the other hand, some items not covered in the drivetrain warranty can get expensive pretty quick. Air Conditioning, for example.

One other thing to consider - the '05 Xterra is fairly much new from the ground up, so there's not much previous experience to base the reliability on.

What you might do is hold off and apply for 3rd party warranty coverage towards the end of your 3yr/36k warranty period.

With that all said, we went ahead and purchased Nissan's Gold Plus 5yr/100k warranty with no deductible on my wife's '04 truck. That added about $1800 to the price, which was discounted over $4000 off of sticker, so even with taxes, etc., we only financed about $22k.