There can be some problems with 10, so if you do switch, make sure not to get rid of your other OS's files so that you can revert if you need to. That said, Windows 10 has been AMAZING for me personally. Yeah some things don't make sense (like the 2 control panels), but I like that it doesn't have the "start screen," that there is a start menu, and I like Cortana, too. Sometimes when my computer is having an issue that's slowing it way down, using the voice command to get Cortana to open the control panel or something comes in very handy. Also I used to have trouble on Windows 8 and 8.1 with the charms bar constantly popping out when I'd be typing and just start opening random apps of its own accord, so I'm glad to not have that issue anymore. Microsoft Edge is nice too, helluva lot better than Internet Explorer, although, of course sometimes Firefox/Chrome/Opera/etc. is still preferable.
In general, I like 10. To be honest, I sometimes forget how to even use 7/Vista/etc. since it's been so long and 10 is a LOT better than 8/8.1 imo. But, it's not for everyone, and some computers have serious issues because of the update... some have driver issues as a result, some just crash entirely, etc.; so it's a risk for sure, and you wanna be positive you can revert should anything go awry if you do decide to go for it.
As for the concerns about spying; I read the clause in question and to be honest, many services these days do the same thing, and if you're using an outlook email address Microsoft already has access to your email anyway (I personally have 2 outlook email addresses). Considering you can opt out of the stuff, I really don't see an issue with it as it sounds like they're mostly doing that to protect themselves should you do anything illegal.