It's only a developer preview yet so I can forgive alot of things in this version, but reading the MSDN blog post "Evolving the start menu" makes it look like it might stay this way (even tough, I think it will have to be changed by populare demand)
Luckily there is a workaround for this!
It's an registry setting that just need to be change. Often this kind of registry hacks requires the creation of a new value, but this alread exist and can be found under:
The Value to change are "RPEnabled", change this to Value data: "0"
You don't even have to restart just push the start button and you are back in the good old days
If you want to use the new "Start Screen" instead every now and then just use the Windows button, or to permanent switch back you just change the registry value back to "1"