This is not an April 1st thing. I have the Windows 8 Consumer Preview and no, it doesn't have a start menu and while you can switch to desktop mode, you can't really avoid the Metro thing.
Here's why Microsoft is doing this - they want to turn the PC into a kiosk device/consumer appliance that runs only preapproved apps from the Microsoft app store. That way Microsoft gets their 30% cut, they get to decide whether developers are even allowed to sell certain apps and finally they get ad revenue from ad-supported apps.
Also, since Microsoft doesn't have a prayer of gaining any significant market share in the mobile/tablet market, they're hoping that by forcing desktop users to use a mobile/touch UI, they will be inclined to choose a Windows 8 based device when they buy a mobile or a tablet.
In order to achieve this, Microsoft has to force the new UI on the users - that's why there is no start button and you can't get away from Metro, even if you only want to use desktop mode.
Microsoft's overall message is that desktop is dying, corporate customers are becoming irrelevant and they're willing to bet the company on this.