Most cars nowadays are pretty reliable. The 370Z has been out long enough that most of the major problems are well-known. But every manufacturer puts out the occasional klunker (see DE.50's comment above).
As with all insurance policies, it just depends on your circumstances. I can't afford a big repair bill so I usually get an extended warranty. I don't remember ever having to make use of them but I sleep better knowing I have them. YMMV
|