2) ACT! works just like a bought one, including synchronising over the Internet with the database in the office. This also means that SQL Server works. I have had inquiries from people who had been assured that Windows 10 would break ACT!.

3) All Adobe programs that I regularly use (Photoshop, Bridge, Acrobat) work perfectly.

4) The programs I use for web site maintenance (MS Expression Web, Xenu for link testing, the ones I use to compress image files, WS-FTP for site updating) work properly.

5) Norton Antivirus could not perform virus scans. This was fixed by reinstalling the program, so it could have just been "one of those things".

6) I've had a look at the new Edge web browser but it doesn't allow extensions yet, so I'll stay away until both Norton and Lastpass can hook themselves in.

7) I do not miss having to locate the top right of the screen in order to shut the machine down.

8) I must have had a Home version of Win8.1 on this machine (it came with the computer) so the upgrade has also installed as Home. As far as I can tell the only thing I've lost is the ability to manually trigger a Windows Update. This is not really a problem on this machine but will annoy me mightily if the same thing happens when I upgrade a Win7 Ultimate box.

9) Utility programs like Advanced Uninstaller and Smart Defrag do just what they are supposed to do.

9) Entertainment works very well. VLC shows movies and iTunes plays music. (I seem to remember complaints from Apple fanbois once about an OSX upgrade breaking iTunes. Schadenfreude.)

10) All programs associated with email worked without any problem. (Pegasus Mail, which I had been told wouldn't work, Benign, which deletes possibly damaging content before messages are delivered to the mail client, Mailwasher, which identifies and removes spam from the server, and of course Outlook and the fixed Norton Antivirus.)

11) Apart from the glitch with Norton Antivirus, the only problem I encountered was when I connected my television set using the HDMI outlet. The TV was recognised as a second screen, but screen resolution was set the same for both screens (the TV is 1920x1080, the laptop's built in screen is 1366x768). It took a bit of fiddling with various settings to get both screens displaying correctly, with the final annoyance being that things were huge on the TV. A slider allowed the size to be reduced from 150% (no, I don't know why) to 100% and everything now displays as it did before.

Overall it has been a satisfactory experience. There's not a lot of new stuff to learn and anyone familiar with Win7 or 8 will be able to switch without any complaints. That won't stop the complaints, of course, because complaining will only stop when the sun goes dark. So-called experts telling you how horrible it is or how the upgrade wrecks everything can safely be ignored, but a backup before upgrading is always a good idea.

Update:

I reverted the Acer laptop back to Windows 8.1. This was because a nuke'n'pave was required to create a clean environment and the only reasonable way to do this was to use the recovery system delivered with the computer. I can update to Windows 10 at any time, but there is apparently a common problem with the drivers for touch pads. The upgrade is not urgent so I will wait until Synaptics and Microsoft sort out the problem.

The upgrade from Windows 7 to Windows 10 on my main computer went off without any problems at all and no problems have appeared in the many months since then.