I would tend to agree that Lexus cheapens the Toyota lineup and Infiinity cheapens the Nissan lineup.
After seeing both the 350Z and the Inifity version, I feel that the 350Z is the weaker car. I also know that the Infinity "SUV" seems to be a lot nicer than the Nissan version. I'm not very familiar with Toyotas (other than the MR2), but I don't know of a nicer Toyota than a Camry (is the Solara a Camry package?). But there are plenty of nice Lexi (plural of Lexus?) around.
It frustrates me that the Japanese carmakers, rather than fighting the American stereotype of econoboxes, instead choose to rebadge a given series of cars to an imaginary make. It is also insulting to me as an American that Japanese automakers apparently have so little regard for our intellect, that they think they can make a change like this and fool the American public. The fact that they for the most part can is not reassuring.