Three PCs waiting for Windows 10 upgrade

At the moment there are three PCs at home waiting for Windows 10 upgrade. They are all in different situations:

• Acer Iconia W510 (touch screen device) was once delivered with Windows 8. When Windows Insider Program started, I decided to let Windows 8/8.1 go and installed Windows 10 Preview on Acer. Ending up to pre-version 10240 Acer is now waiting for the final version of Windows 10. And of course after that Acer will continue to receive (infinite?) updates so the Insider-story goes on and on...
• Dell Latitude E6420 is running Windows 7. It has many accounts and a lot of applications installed. It will be interesting to see IF Windows 10 runs smoothly on top of Windows 7. It was never advised before to do it that way...
• Acer W4-820 is my Windows 8.1 -based tablet. I want to see two things: a) how Windows 10 installs on top of Windows 8.1 b) is Windows 10 made for touch screens or not (I guess it's not)?

So, Microsoft. Let loose! Gimme that operating system! I promise to wake up early in the morning (European time) to see if you have passed me the chance to install your new software.