Things I like:
In use the operating system does everything that Windows 7 did for me but feels a bit more polished and up to date. The interface is cleaner and looks prettier.
I love the new Task view button. This instantly displays all open applications in a tiled format which is much more useful than the carousel format that win-tab gave in Windows 7. As a bonus the Task view also allow you to setup and maintain multiple desktops. AMD and Nvidia graphics cards have provided similar features for some time now and I have never felt the need to use them but now that it is built into the operating system I might be more inclined to experiment.
I love that ability to snap to corner as well as snap to edge. Snapping a window to a corner puts it into a quarter screen allowing you to easily tile your screen with four distinct windows.
I like that the new metro style interface is better integrated and also seems to have more functionality than Windows 8. In Windows 8 metro always felt like a barrier you penetrate to get to the real control panel behind. Windows 10 still has this "real control panel" but I find that the metro settings menu does everything I need.
Things I am not sure about:
I still get some unpredictable behaviour when I restart. It is hard to pin down exactly because it is unpredictable and not reproducible but on various occasions my second display and my Logitech G19 keyboard have not recovered correctly from a reboot. This may be related to a lack of stickiness have noticed from system tray icons. Some applications don't appear to be minimising to the system tray to run in the background as I expect. Again this doesn't appear to be consistent or predictable.
Microsoft's voice assistant Cortana is not available in my language (English with an Irish accent I guess) so I haven't been able to try it out. To be honest I have no desire to talk to my desktop in any case. I occasionally speak to Google Now on my phone for the novelty (usually to see if it can finally understand the Gaelic pronunciation of my daughter's Irish name) but I don't use it for any practical purpose.
There appears to be some compatibility issue with my choice of anti virus programmes: Avira. Neither the system tray icon nor the Avira control panel would appear for me in Windows 10. Task manager suggested that the scanning routines themselves were still working but without any visible user interface I couldn't be sure. I have temporarily returned to Windows built in antivirus: Windows Defender.
A lot of the new integrated environment features (Outlook email, Edge Browser, Windows Calendar etc) are not really any use to me because I am already a committed Google user. Windows 10 does offer integration features so you can link your gmail and google calendar etc to you Microsoft ones but I don't want to use use outlook to access my gmail I want to use gmail. I don't want to use Microsoft calendar to access my google calendar and so on.
The Windows store doesn't appear to have apps for some of the services I use. There is no Feedly client for example. Instead Microsoft offer their own Flipboard. The biggest omission though is:
There are almost no official Google apps in Microsoft store. Where is the offical Gmail app? Where is the official Google Calendar app? You can access all of these through Chrome but that feels a bit disconnected from the new integrated Windows environment. I did manage to put web shortcuts to gmail and google calendar onto the metro start menu but that required a tortuous multi step process involving the google task bar and an intermediate desktop shortcut.
A thought about Microsoft and Privacy
I have read a few articles expressing concerns about privacy in Windows 10 but having considered the situation I am happy to tick all of the boxes allowing Microsoft to spy on me. Some years ago I grappled with this issue in relation to Google and I realised that the benefits of all these free services outweighed (for me in any case) the loss of privacy. While I am delighted to get Windows 10 for free I do realise that Microsoft need to earn money somehow and if my allowing them to show me a few targeted ads is the price then I am happy to allow that. The problem as I see it though is that Microsoft are already too late to that party. Everyone I know is already fully committed to an existing information eco system. Microsoft are aware of this and do appear to offer seamless integration into their own apps but this means is that they are getting data second hand from Google or Apple or Facebook. I don't see how they can ever catch up.