Everyone wants to be the Netflix of games. Microsoft has Xbox Game Pass, Sony has PlayStation Now and publishers like EAhave plans to start offering their own subscription-based services as well. Contrastingly, it seems Nvidia wants to exit the game streaming market--the company intends to bring its GeForce Now services to its Shield TV set-top box and desktop platforms to exclusively offer remote access to its high-end gaming hardware.
GeForce Now currently exists as two services. The first allows Shield TV owners to stream and purchase games from Nvidia's partners. The second allows PC and Mac owners to play the games they already own through Steam, Uplay, Battle.net and the like while remotely tapping extra power from Nvidia's GPUs. (This also lets Mac owners play Windows games without Bootcamp or virtualization tools.)
The end result is the same--Nvidia streaming a game to whatever device you're using--but the method of acquiring those games differs. Opinions will likely be split on the issue. Some people are fine with simply renting a game from whatever service is available to them, or purchasing through an unproven storefront. Others want to be able to access the all-too-costly library of games they've amassed over the years in one place.
Nvidia appears to prefer the latter arrangement. That doesn't come as too much of a surprise--the company is known for making GPUs, not selling games. Chances are good that many gamers are more interested in owning a game than renting it, especially on PC, where the amount of storage they can devote to their game libraries is limited only by the weight of their wallets. (Or, you know, the limits on their credit cards.)
Some people are also done with new platforms. It's frustrating enough having to install Steam, Uplay, Origin and Battle.net to play all the games you own. Having to go through Nvidia just because you own a Shield TV or don't want to install a beefier graphics card is a tough sell. As Valve is hoping with the new Steam Link apps, people might be more likely to use a service that allows them to access their existing library.
PC streaming platforms also don't have the luxury of exclusivity like Microsoft and Sony. Microsoft and Sony decide what is or isn't allowed on their consoles--and in Sony's case, the other platforms on which PS4 owners can play certain games--so they have a natural edge in creating subscription services. They publish some of their consoles' exclusive games too, which gives them even more control over where they appear.
GeForce Now is currently available as a free beta for PC, Mac and Shield TV. It offers access to more than 200 games, some of which have been optimized for the service, and you can find the full list of supported titles here. Nvidia hasn't said when this iteration of GeForce Now will exit beta or how much it will cost when it does. If it's anything like other services, pricing will likely depend on your virtual setup and time spent playing.