I installed 10 the first week of October and have not been back to Windows 7 since. And I still support Windows 7 six to eight hours per day, waiting for activity to heat up over at Ten Forums.
Ten so far nearly perfectly balances the best of Windows 7 desktop with Windows 8's touchscreen interface. With Continuum if you install to touch it will push more of those features including apps, without touch it will give what I have which is a real, perfectly-functioning Start Menu with sample apps pushed over to the side to trial, ignore, hide, or uninstall. I like having my five web mail boxes in one Mail app with large reading pane, the Contacts and Calendars that merged, Skype, OneDrive and Reader. I may not want any more but I've promised to try them all.
I'm waiting to see how they resolve the even split between Win7-type Control Panel and Win8-style PC Settings since I always reach to get the more familiar 7 interface. They may and probably should keep both.
I've always believed SIW2's theory that they stuck so long with WIndows 8 because they'd rewritten their business plan for subscription apps including the OS, but from what I saw at MVP Summit they are trying to strike the right balance without blinders (like not recording metrics of those installing Start Menus in Windows 8). They are actively reading your feedback, especially that channeled into the Insider Hub in build 9879.
As one of Windows Eight's strongest critics brought into a special Focus Group at last year's MVP Summit along with other top Forums' producers to tell MS Execs where they went wrong, I am thoroughly pleased with MS's new direction with Windows 10. A big part of that was due to our former MVP lead and Brazilian wunderkind JP Clementi who was so instrumental in speaking truth to MS powers about this that he was promoted as our liaison to the Windows 10 Product team. Things have really changed since we whispered between ourselves about Windows 8 at past Summits, having been told they didn't want our feedback.
In order to mess this up now, the extremely bright and motivated Windows 10 Product Team would have to take so many left turns that we'd all fall off. Instead I look for steady improvement, although that's hard to imagine since settling into this Preview it feels already like a finished OS and I will not go back.