My X with 1,200 miles on it is in the shop for engine repairs. There is no timetable for its return at the moment. By no means is my experience even remotely typical. The VQ40DE engine has every sign of being an excellent powerplant. I just got the bad apple (err... lemon).
That being said, I have been driving my 1997 Jeep Cherokee Sport 4X4 the past two weeks. I find it ironic that it's the vehicle that's running right now, especially with 98,000 miles on it. It still runs strong, crosses water a third of the way up the doors, chews up any trails that I take it on, etc., etc.
I bought the X thinking that I'd have a more "reliable" vehicle. I'm now rethinking that idea. My Cherokee has had no major problems, and best of all it's so simple that I can work on it myself. Yeah it's shaped like a brick and cannot safely be driven over 75 MPH, but who cares? It's paid for and runs great.
My biggest problem with the X is the treatment that I've received from Nissan. I've talked to three levels of their customer relations management, and they don't give a damn that they sold me a flaming POS. In as many words they've told me that "shit happens." This is the last Nissan I will ever own. It's sad because I actually like the X.