IMHO the only answer is YES
I use an iMAC 27" with 2.8 GHZ quadcore CPU and 16 GB RAM and the workflow that I am used to with my old D700 is remarkably slowed down. The preview in LR4 takes much more time to render the thumbnails as well as when I open a single photo.
Same what is mentioned in the article when it comes to more than 4-5 layers in PS5 (PS6 seems to be faster but I only upgraded recently).
So - for me the only solution is to be patient since the iMAC is not even 2 years old and I don't want to burn more money which means I may consider purchasing the next generation. But, to be fair and honest, this was expected when I bought the D800.