I've already made the jump since long ago, and the train's (the non-hatetrain) is getting better. Though I've had some issue, it was minor and I fixed it with a user change. Apparently me cluttering the system as usual to the point of slowing the boot, but that was fixed by a reset. Anyways...
*That telemetry everyone's nagging about? Not a problem. As has been stated multiples of times, it's just sending anonymized crash log data and what not, and that can be controlled. You can take a look here for all of the hard details;
http://www.zdnet.com/article/windows-10-telemetry-secrets/?tag=nl.e539&s_cid=e539&ttag=e539&ftag=TRE17cfd61 *Only a few apps actually complain about compatibility. Some of course are lost, but that's natural with each version of Windows. Even Dust: An Elysian Tail which is supposed to be incompatible with Windows 10 at least as reported on GOG, I actually played the game and beat it with almost all of the extra stuff if not all. Your mileage may vary, if especially you rely on a legacy app or you often play a legacy game that'd it be a deal breaker, but for me, it hasn't, and it only hurt me on the subject of being able to install and play FF8 the old disc version.
*The UI has been going up and never down. This time, you can use either a Start Menu or a Start Screen, all with a really modern interface that is less about pixelated curves and more about actually looking great on PCs. I refuse to go back to the Start Menu at this point.
*Advertising inside the OS? Bullshit. If it were advertising, you would have never been able to disable it. Behold what I just said. You can disable those app suggestions, which by the way, can be accessed with just a mere toggle in the settings. That's all it needs if suggestions about which apps to obtain aren't your cup of water.
As for games with SecuROM, that is a bit of muddy water at the moment for some reason. I can report being able to play Leisure Suit Larry Box Office Bust, and with SecuROM DRM ON WINDOWS 10.
Up until now, I haven't seen really legit points to not consider Windows 10, apart from:
*Automatic updates
*GWX, which by the way, is not related to Windows 10 itself (besides acting as the downloader for it), so counting it in as a Windows 10 disadvantage is sort of misleading. Call it a Windows 7 or 8.1 disadvantage.
If you're still hesistant on whether to upgrade or not, ask me whatever you want. My Windows 10 system is right within hand's reach for me.