Stable or Not, make a nice Restoreable image of your Current OS. then either CLEAN install or upgrade Install. I have done both.. upgrade takes longer, but then you do not need to install all your pinker toys... well I had to Repair office 2013. but that was all. Restore you old OS if you do not like Win10 v9860 or v9841
I have an Acronis image of my win 8.1 so I don't care if the O/S goes nuts in a future build. As for the keylogger, if they find something on my machine that can make their bread rise faster, go right ahead. At least it's better than dealing with some internet thiefs that don't really leave me a choice of what I want or don't want to install. I wonder if they noticed that I can't use the windows feedback app. Of course they know, they can see everything.
24 hours ago, I would have written about how the first build (a milestone build) was at least as stable as 8.1, and how 9860 (an interim build) was itself stable but caused apps to crash left and right (notably MS ones, like Skype and Outlook 2013), but unless I've just been astoundingly lucky over the last day and a half, I think I know what caused my several days of app misery: Hyper-V I don't mean that I'm running Win10 in Hyper-V but rather that I merely had it enabled on the host system for occasional use running a VM. Having it enabled wasn't a problem in 9841, but it sure was in 9860, at least here. Hyper-V changes some fundamental things on a host system, and it seems that on my system anyway that was a problem. Now that I know which build of VirtualBox works in W10 (4.3.12), I won't be trying Hyper-V again until perhaps the next milestone build.
ehh well. I'd say its stable enough, I might even throw it on another HDD just for kicks. they've seemed to fix issues pretty fast in their updates (I kinda just stick with whats working and not update tbh)... its entirely up to you
In my case the 9841 was much better than the 9860 and I ended up going back to 8.1 as Main-OS, because I had just too many random crashes when I was gaming, which can be quite frustrating if you are close to finish a map in D3:RoS and have to do it over and over again after a crash.