In the long run I imagine it will become "the" OS that Windows 7 is. According to Microsoft 10 is the last major OS release they will ever do. From now on they will simply build upon 10 and make it sort of a "cloud" SAAS type thing. I downloaded and installed it on one machine just to see how it is going to be and I can tell you already there are some things I very much dislike. I was honestly pretty shocked at how non-business and how invasive it is with your information. I did an in-place upgrade on a domain joined Windows 7 Pro machine. This is a domain joined machine and is considered and enterprise type installation (domain joined desktops do not even ever see the Windows 10 free icon or anything, you have to manually download and install it). Any edition below pro for example, is going to get Windows Updates downloaded AND installed whether you want them or not. Its not optional.... even on pro and enterprise editions you can only "defer" updates for a period of time. Updates are distributed ala "torrent" style and you are not asked if you want to participate in helping with the bandwidth.... It is VERY invasive with the default settings opting you into all sorts of data collection about your system, your use, your surfing habits, location, etc. Granted a lot of this mess can be turned off but you will have to dig and spend some time doing so. Big corporations, oh yeah.... .they are going to be thrilled to see that Xbox and Microsoft's cloud storage and whatnot are installed by default and really you cannot even uninstall them (if you are very technically inclined with using a powershell command prompt there are ways to uninstall some of this but its is not in add/remove programs or windows features). I'm sure big corporations with many many thousands of desktops want all their employees looking at Xbox crap and potentially having their company data getting uploaded to some cloud storage. I'd wager that MS will very quickly have some enterprise deployment tools available that will allow one to strip all of the non-business oriented crap out of a build. As it is right now, it is very far from being a "business" oriented operating system. Everything about it screams at you to waste time screwing around on the web and to not do anything business related.
Overall my impression aside from that seems "okay". It will take some getting used to finding things. Some things like the traditional control panel are still there but deeply hidden, they want you to use the newer one which leaves a lot to be desired.... I have not had much time to really "use" it much yet so my overall impression as of yet is not really inclusive. I imagine it will be quite some time before all of our programs are "certified" to work properly on it. Flexi just might install and run just fine but that is useless if your Mimaki or HP or Mutoh, etc drivers will not install or load.... It just still way too new and early to really try and trust it for running your business on. As already mentioned, its going to take some time for this initial release to get a full shakedown in all industries and get the initial bugs worked out. Probably will be some time before the first major service pack update before it really starts to mature into something stable and solid that you want to deploy for your business systems. Eventually Windows 7 will become outdated and stale much like previous OS's have and one day it will even become totally unsupported and no longer updated like XP.