Those who really want to get it immediately can do so by proactively downloading it from the Software Download site or using the Media Creation Tool. The bits are also available via Windows Update, Windows Update for Business and Windows Server Update Services (WSUS) as of today, April 11.
As officials said: "This (manual download) option is recommended for advanced users on devices running a licensed version of Windows 10."
Users who are willing to wait for Creators Update to come to them will have the ability to set a convenient time, hold off for a few days, and/or expand the "active hours" window during which the release won't be pushed.
Eligible Windows Phone users who want the Windows 10 Creators Update will see the rollout of that release begin on April 25. Volume licensees who normally get new Windows releases through the Volume Licensing Service Center (VLSC) will be able to get Creators Update starting May 1 via that channel. Windows 10 Creators Update was available to MSDN/TechNet subscribers as of last week.