I had to use it for Gears of War 4 and Gears of War UE. My experiences:

• It’s taking half an hour to start the download. What the fuck is it doing?
• Oh good, it’s almost installed. Oh it paused for some reason? No problem I’ll just resume- oh, it’s just restarted the whole 120GB download.
• I’ll restart my PC because Steam can pick up where it pauses between restarts and surely Microsoft the creator of the fucking OS can get something basic like that correct- oh I guess not.
• Oh sweet an update for Gears, oh wait no it’s redownloading the entire game to apply the update.
• Why isn’t the update downloading? Oh support is telling me I need to uninstall and reinstall the game. Oh that didn’t work this time and instead I need to enter an obscure wsreset command instead?
• What do you mean I can’t access the game folder to look at the files?
• Why isn’t the game launching any more? It’s just stuck on the splash screen. Oh the store says it’s corrupt? It needs a full redownload again.

Not to mention the issues with Microsoft sign in/Teredo once in-game.

The Xbox app has the same issues because it’s just a differently coloured UI over the same APIs. They’ve had multiple decades and still can’t get the basics right, I think Steam will be fine.