Since that's in the trade-in value range on
http://www.kbb.com for a basic Q in somewhere between "good" and "excellent" conditon - I would say on the surface it's a very good deal. Has it had any body or paint work? Have you seen the service records? There are a lot of things to consider... Is it at an Infiniti dealer? Can you get the extended warranty? Assuming the oil and other fluid maintenence has been good, the car should be good for 150-200K with excellent maintenence...
Heath