mrjones makes a great point.
And to a certain extent, I agree with you about the re-badge job on these cars. They could've done a much better job to distance/distinguish these cars from their Nissan counterparts. This is one thing Lexus/Toyota does extremely well and Honda/Acura, too. Even dating back to ES 250 days, they did a lot to differentiate it from the Camry. They even put frameless windows (signature ES design although not anymore) on those.
However, I wouldn't go as far as to say these cars were mistakes and solely responsible for cheapening their image. Despite the re-badge job, the I30's were cash cows for Infiniti before G35's came along. Also, despite subtle differences between it and the Maxima, you will be surprised how most people don't know that it's the same car.
As for QX4, these were slow sellers and I wouldn't blame solely on the subtle re-badge job. If Lexus can pull it off with their LX470, why can't Infiniti?
So then what really cheapened their image? There are many factors (poor re-badging job is part of it) and I think it's more to do with quality than anything else. Sure, the engines were alright (most notably the VQ engine) but the materials that went into the car, especially in the interior were cheap quality. The type of materials they used on these cars were unacceptable for a luxury car. Best example is its flagship, the Q45 (the only car that's not re-badged). You should take a look at the interior. They put the same radio unit used in cheaper cars like the I30/Maxima and others. When I see that, it's hard to justify paying $50k for it when I can easily get the Lexus. No wonder it was such a poor seller.
As for them using cheap materials, I can understand their situation to a certain extent since they were in trouble financially at the time these cars were built. And also because of the same reason, they probably couldn't go any further than to simply re-badge these cars.
They've certainly improved in that department the last few years starting with the M35/45 and now with the new G35.
One interesting fact. The Infiniti I30 (aka Cefiro) design is what's known as the Maxima in other countries whereas the Maxima design that you see here is only available here. So it's actually Maxima that was re-badged.
