And those processes and threads will run faster on a four core machine than an equivalent eight core machine. Keep in mind, going from four cores to eight cores does not buy you any extra transistors - it's the same number of transistors. What it does do is introduce extra cache contention, and likely smaller caches. It also introduces extra layout complexity.

Most laptops / desktops perform much better with at least two cores than one core. Particularly if you have a CPU hogging process - your UI can't remain buttery smooth interactive. There is even some argument to be be made from going from two to four. (Background application like a render, plus another App doing something nasty killing your CPU - you can still launch activity manager and kill the errant task).

But, It's not clear to me there's any value for the client for taking a four core machine and breaking it up any further as opposed to taking the increased transistor budget and improving those existing four cores.

Remember - the tradeoff is not "Do we want more, faster, transistors" - of course we do. Rather, the tradeoff is do we make smaller, lower cache cores, or do we make larger, bigger cache cores.

The evidence tends to suggest for the near future, that bigger cache, faster cores are the way to go on your average desktop/laptop.