I took the plunge and upgraded my main Toshiba laptop from Windows 8.1 to Windows 10 a few days ago, just after it was released.
I had a difficult experience during and after the upgrade, due to the buggy AMD Radeon video graphics driver provided with and installed by Windows 10. The AMD driver would randomly and frequently crash Windows 10 with the Windows 10 equivalent of BSOD (Blue Screen of Death), listing the cause as "INTERNAL_POWER_ERROR".
I used my other laptop (a Toshiba netbook still running Windows 7) to research the error and found out that many users whose laptops had Intel + AMD dual video graphics were experiencing this issue after upgrading to Windows 10. The cause was confirmed to be the AMD drivers installed by Windows 10. Uninstalling the new AMD driver and installing an older driver known to work was not an option, as Windows 10 automatically upgrade the driver again via Windows Update, after which BSODs occur again.
The only workaround noted that actually works is to disable the AMD Radeon graphics adapter in the Windows Device Manager. I was able to boot into Windows 10 after the upgrade crashed 4-5 times. After booting into Windows 10, the computer would run less than 5 minutes and a BSOD would appear again.
Windows is very sluggish immediately after logging in, so it was a race against time to get the Device Manager to open before a BSOD occurred. It took a few tries, but I was finally able to get into the Windows Device Manager and disable the AMD Radeon graphics adapter. A BSOD occurred soon after I disabled the AMD Radeon adapter, but after another reboot, the AMD Radeon adapter remained disabled, and I experienced no more BSODs.
I periodically checked the AMD Radeon graphics adapter in the Windows Device Manager and clicked the "Upgrade Driver" button to see if a new driver had been released. Windows kept saying I had the most recent driver installed, dated 07/15/2015. Yesterday, Windows said that a new driver was available and it immediately downloaded the driver, installed it, and re-enabled the AMD Radeon adapter. The new driver, dated 07/28/2015, appears to be stable as I have not experienced any BSODs after the AMD Radeon graphics adapter was enabled with the new driver.
I have not been a fan of the Windows Start Menu since Windows 7. Stardock Corporation made a neat little app named "Start8" for Windows 8, to restore the Windows 7 start menu to Windows 8 and 8.1 systems. The app costs only $4.99. The Start8 app has been updated for Windows 10 and named "Start10". I can't recommend the Start8 and Start10 apps enough.
With the new AMD Radeon graphics driver, my upgrade to Windows 10 was finally successful, and with the Start10 app, the Start Menu is not an annoyance to me.
Bonus tip: I found out that pressing Win + X (press the 'x' key while holding down the 'Windows' key) pops up a handy little menu to quickly access Windows computer management functions.