If you buy Call of Duty: Infinite Warfare PC from the Windows 10 store, you can't play with anyone on Steam
Call of Duty: Infinite Warfare on the Windows Store is a bad bargain.
Don't buy Call of Duty: Infinite Warfare from the Windows 10 Store.
I wouldn't normally seek to influence your purchasing decision, but a recent update to the Call of Duty: Infinite Warfare Windows 10 FAQ at Activision Support has revealed a pretty damning little quirk of this specific version.
Basically, if you have the Windows 10 version of Call of Duty: Infinite Warfare, you can only play with people who also purchased their copy from the Windows 10 store. Those who bought from Steam, or bought a code or boxed copy and activated it through Steam, will be excluded from matchmaking with you. The restriction applies to Call of Duty: Modern Warfare Remastered, too.
I hope I don't need to explain how detrimental this is likely to be. Whenever you build barriers and split the audience for a multiplayer game, you're chopping off its legs. The smaller the pool of people you have to play with, the longer it takes to find matches. The less competitive the scene becomes. The shorter the lifespan of the game.
While you might argue that this restriction affects Steam users as well, cutting them off from potential teammates and opponents using the Windows 10 build, the Windows 10 audience is almost certainly going to be much smaller than Steam's. Steam is the dominant PC platform, hands down. Windows 10 Store buyers will definitely get short shrift.
One can only hope this is some sort of tragic error and will be corrected either before or soon after Call of Duty: Infinite Warfare launches later today - for the sake of those who might have already purchased from the Windows 10 Store without knowing of this rubbish restriction.
I assume this situation has come about because of some restriction on the Windows 10 Store for third-party games, but it doesn't make a lot of sense for end users. Call of Duty: Infinite Warfare doesn't have cross-play between Windows 10 and Xbox Live, so there's no actual benefit to purchasing the Windows 10 build as far as I can see. Amazing.