I, too, followed the original instructions and played the Witcher 3 and Ark: Survival Evolved via my mac against an AWS instance on the frankfurt datacenter. This was in Vienna which means that the average ping was around 40ms.

It was a fun little project to get it all working and it was playable but barely.

The added latency makes you feel a little floaty (like a bad VR experience - the kind that make you sick). The witcher looked good when you stood still but not while moving. Ark's performance was abysmal on the aws hardware such that I had to turn down the settings.

Part of the bad experience is likely my ISP's fault - I had spikes of packet loss - though I think this is fairly typical.

The cost is mostly not in the spot instance (that /is/ cheap) but in the storage (EBS) that you need to keep around to mount a spot instance whenever you want to play. The bandwidth cost is non-trivial for the amount of data you're streaming. I had about a 40 euro bill for the month under somewhat light use.

In the end, I can't say I recommend it. Onlive and Gaikai didn't do so well. That might have been their business models but I believe the tech is equally to blame. It's a ridiculously hard thing to get right consistently.