I've always re-upped when the $1 deal is available. I've played a ton of games using it. Right now its only for new users, but the $5 deal is available if you get 3 months. I went ahead and bit the bullet there so I could start getting my Games with Gold again, and then it ends up being like a $15 3-month rental for The Outer Worlds.
I have like a half dozen games I could play right now with Outer Worlds tomorrow, which is pretty great for the price. After I'm done with them, it probably wouldn't be an every month thing, but this would get me to play games I'm otherwise waiting on a deep sale for or weren't really super interested in, but was curious to check out. Like if I had bought Gears of War 4 cheap, I probably wouldn't be super interested in Gears 5 as the gameplay isn't really that great I'm finding, but knowing that Gears of War 5 is practically free for me, there's a good chance I'll check it out.
I'm really curious to know how developers and Microsoft actually make money off this, especially with new games getting put on it.