There's not really any big deal surrounding hardware or software issues with win10. The issues that have been focused on so far is privacy - you literally cannot turn off sending data to MS. And to a lesser degree the unclear revenue stream for MS because they gave it away for free to most people. (Those issues are probably connected, obviously). There's a vocal group on these forums that take these issues seriously. But if your question is just "does it work?" then the answer is pretty much yes.
There shouldn't be any reason to be unclear about the revenue stream. Yes MS gave Windows 10 upgrades away for free, but only to people running Windows 7, 8 and 8.1. If you had Vista or XP then you were out of luck. If you had Linux or OSX, then you didn't get it for free.
Android, iOS and some form of yet to be deployed cloud computing (wirelessly attach a keyboard, mouse and monitor/tv/vr display to your cloud watch and then it streams everything to the servers, including 4k/8k games) are threats to windows in the future. However, older versions of windows are the biggest current obstacles for Microsoft moving forward and innovating so it can compete with those other platforms. According to the July 2014 Steam Survey, Windows 7 64 bit was on 49.92% of Steam computers, and this is two years after Windows 8 had came out.
Even with the October 2015 Steam Survey you get
Windows 7 64bit - 36.67%
Windows 7 32bit - 8.19%
Windows XP 32bit - 2.26%
Despite the free upgrade and Microsoft pushing hard windows 10 64bit is only 26.42% (windows 10 32bit is 1%)
It will only help Microsoft by upgrading every possible computer to windows 10, especially when it can help leverage its windows 10 user base to get developers to create Windows 10 universal Apps which will run on PCs Windows 10 phones and even the Xbox One. Just this week, windows 10 had it's fall upgrade, the Xbox One upgraded to the New Xbox One Experience, which means a new UI and Windows 10 on the Xbox (giving MS another 10+ million windows 10 devices) and Windows 10 mobile will launch in the next month. I think Microsoft gave up between 500 million to 2 billion in upgrade revenue to push the windows ecosystem forward.
Though Microsoft also shot itself in the foot with the privacy options and lack of update notes. I use Windows 10 and think it is a better OS than 8.1 or 7 and I get what Microsoft is trying to do, but they really hurt themselves with those two things. Besides those two complains all I hear is that some older hardware may give people trouble and then the media center faithful are highly upset about not having an upgrade path on windows 10.