Game Pass is an amazing service. I converted 2.5 years of Gold for $1 and then extended 6 months via Microsoft Reward. I expire in December.
If I were a kid, for $300 and $1 subscription for the first month, you could have a boundless library of games and not pay another penny if you get in the habit of Microsoft/Game Pass Rewards.
As an adult, I'm somewhat reminded of my brief time with GameFly which didn't really alter my spending habits, I just ended up spending a lot more time playing games that I had passing interest in instead of investing more heavily on those purchases of games that I knew I wanted which it turn really burnt me out on gaming. Gampass has some inherent advantage over that model, as you don't feel the need to play every "rental" right now so that you can return that game and get the next thing in your queue.
I still purchased the Ultimate Editions of Forza Horizon and Flight Simulator. I don't regret either. I still have a hard time investing time into games I don't own. Most of my Game Pass time is broken into:
-Game Pass Quests, Microsoft Rewards Activities
-Trying out indie games. This is extremely valuable to me as it feels a lot like when Microsoft made XBLA titles all have demos. It has saved me so much money on 50/50 games that I probably would have purchased and more often than not, would have regretted the purchase. It definitely helps me get past the hype of those types of releases with Powerwash Simulator being the best example.
-Co-Op. A Game Pass friend is a wonderful thing.
The highlight of my time with the service so far was Psychonauts 2. I'll probably purchase that at some point.
I've been sitting on the fence about extending the service. It's been a long, dry period of games that interest me of late. I'm almost thinking it would be better to let it lapse and resub once a game releases that I'm interested in, though I'd have to forgo 3,000-4,000 Rewards Points per month.
If it is worth it for someone else, is debatable. If you've been in the Microsoft ecosystem for a long time, it might be a harder sale though I do think they do a much better job than Sony at a robust catalog of newer titles. I converted 10 years of PS+ since the upgrade price capped off at $150 and I figured I'd get my money's worth over the long haul. Granted that service offering is young. I still think subbing for a few months a year makes the most sense and then you can play catchup on what you've missed. That or waiting to the end of a generation and playing catchup that way.