10 is not as polished as I would expect a released OS to be. Do I use "Settings" or do I use "Control Panel"? Is "File History" meant to replace and deprecate "Backup and Restore", or is it merely a simplified companion to make it more likely that technotards will automate backups where they were intimidated before? Because File History definitely isn't as flexible, and the "Settings" version of File History settings don't always seem to sync with the "Control Panel" version of File History settings. There are other inconsistencies that hint of a transition period of some sort -- the inability to manage advanced settings for existing wifi profiles, for example (although wifi management is much improved over Win 8).
Be that as it may, 10 is ultimately the prevailing force. You can't run Windows 3.1 all your life, you know. 10 will be supported much longer than 7, and as such, will receive security patches and new features for much longer. According to some, 10 is faster than 7. I'm not sure whether that's true. It's not slower in any case. Even though 10 is a work-in-progress, it's still highly stable, aggressively maintained, and capable. All operating systems have their quirks, and most users would not be hindered in the least by those that I've mentioned. All my Windows machines will be upgraded to 10 before the free upgrade offer expires.
The cause for biggest concern is privacy. Turn off Cortana. Turn off location reporting. Turn off sharing data with trusted partners. Turn off sending your contacts to Microsoft so they can improve their Cyberdine T-1 or whatever. For goodness sake, don't auto connect to wifi hotspots just because someone in your contacts has connected to that same hotspot. Don't you know that's how herpes is spread? And the problem with turning all this stuff off is that it could enable itself again whenever you update to a new build -- but the OOBE doesn't run when you install a new build, so you aren't prompted or warned that this is going to happen. If I were a Tea Partier I'd organize a class-action lawsuit. As it is, I just disable all the send-to-Microsoft settings (except for error reporting -- that one stays enabled) as I stumble across them.