In a blog post on the Windows site today it was mentioned that Windows 10 will START to be released in waves on the 29th of July. It appears that those currently in the Insiders Preview (ie. Beta) program will receive the update first and then those who have already registered for the free upgrade. Even then it will start with those that are the most compatible to run Windows 10. Those who are less compatible will be delayed slightly until there is an update to make you more compatible or you'll be given a choice to find an alternative solution for your issue (replace hardware or software) or to hold off on the upgrade to Windows 10.

With over a billion computers eligible to be upgraded Microsoft looks to be making a wise decision to slowly roll out this major upgrade.