First party wise its locked tight for success.

Not so with the third parties who wouldnt want to be forced to program a console exclusive or due to licensing issues.

I can see MS being a decent competitor to Steam in terms of getting people to buy games or get games on their Windows gaming platform over Steam. At least way better than Origin or Uplay.

I welcome it! I already have Steam, Origin, Uplay, GOG, and Desura - and I already have a Microsoft/Xbox account so this would be great for me xD.

I think this will be Nintendo's plan also will be to have one eco system for both their systems since it boosts the install base big time.

If you think about it by MS bringing their eco system together they already have an install base of over 20 million xbox gamers on their store and however many that is/plan on using their windows store. Its like apple with ios, when people look at ios they dont say "ok the is like 20 million ipad owners and 10 million iphone6 users and 20 million iphone 5 users etc they look at the ios install base as a whole this is what MS plans on doing and is also what Nintendo plans on doing imo and this is also why i see Sony launching their own cross platform Digital Store also.

See I would sort of support that idea if they supported WIndows 7-8.1, even then I'm a bit wary because I dislike having too many clients riddled on my taskbar/desktop/start menu which is why I stick with GoG Galaxy, Steamn Origin and Battle.net, I ignore the rest. I don't really like the idea of being told where to game on what to buy from though (I know the same sort of argument can instantly be made at Steam but let's be honest, Steam support multiple OS's and open source modding, MS don't want any of that and want all control so that argument is more of a cop-out if anything).

Microsoft, is bounded with the price, if they price the PC Version on windows store the same as the Steam, so there is no reason in buying the Xbox One version, even receiving the PC Version, you would be paying more than just the PC Version, if you only want the game on PC, and i don't think that people want to own the game on Both Plataform, instead of get it cheaper on the plataform they want.

And if they price it in the same price for the PC, and the Xbox One Version, Steam, will be cheaper (talking about third party games), so PC Gamers, would purchase on Steam, insteady of Windows Store, and the Third Party companies will not stop of supporting Steam, only because Microsoft, started to support their Store, the Third Party, will Support the most number of Digital Stores on PC as possible, because they don't need to make another port to launch on other Store, just need to get the license to launch on other store.

I Want to know how Microsoft, will price the Third Party games on Windows Store, to try to compete with Steam.

The thing is as well is that not only would MS have to  court all those devs to sell on their store but also cut down on the fees a bit as well as pull Steam like sales to entice bigger numbers. The fact Steam openly supports modding on their client (you can mod the client, mod most games and they let you mod their own to your hearts content) which MS seems to not even mention or touch upon for their future games. Modding on PC is liki a huge advantage and boon for the platform that MS really shouldn't ignore, Firxis even got some mdoders together to release some mods for XCOM 2 before the game was even released so that mods were ready and working day 1 for the game for those that wanted to change the game a bit and that was greatly cheered and welcomed and sales are apparently doing excellent for them.

MS definitely needs to get pricing right but I wouldn't make the final move if I wasn't allowed any sort of modding.

Indeed. I mean could you imagine the install base the WiiU+3DS would have right now if they where classed as one system??. This is something i really feel Nintendo will have to do.