Something to think about: How many eyebrows or faces twitched of even yells of "WHAT" were released back in June when 29th of July general availability date was announced? Anyone having tried insider preview back then knew 10 is far from being even close to finished.
Now, with the "final bits' on both my laptop and tablet I can confidently conclude that not only it`s not finished but in the present state the OS is no more than beta software. There are countless "inconsistencies" and bugs that were pointed in many threads, apps that do not open or need several attempts to make them work...but that is the point with beta`s isn`t it? IMO the real reason behind offering Windows 10 as a free upgrade is being real beta software, MS probably intends to bring the OS to more mature state in the next year or so and then stop the "free" beta program and continue business as usual.
Maybe 5 million insiders were not enough(myself in that count) and now after the release everyone is becoming an insider wishfully or not even without pressing the "become insider" button, considering that you are obligated to install every update and to leave the feedback to full data send otherwise as explained some parts will not function.
Having said that I`m by no means complaining, it is my opinion on how W10 evolves and a very probable explanation of the real MS strategy.
Actually I`m enjoying 10 on my laptop/desktop version, the tablet experience though is far behind 8.1 as already pointed out and really hope it will eventually improve with lots of feedback taken into consideration. The battery life on the tablet is awful despite fresh OS reset and disable all background programs and Wi-Fi during sleep, this may be a sufficient reason for reverting to 8.1