I've done this process. Users will have to logout and login since the username/email of their current account will be changed to "@icloud.com" account. Users will be the owner of these accounts.
In terms of experience, it's good from an admin perspective to say "everyone just has an Apple-ID", but from a user perspective some stuff are a bit confusing. For example, managed Apple-IDs can't download applications from the Appstore. All app downloads must be downloaded from self service or deployed by IT. This isn't really "bad", but we have some users who use their account on unmanaged devices and they get confused about the whole "business owned devices" vs "personal devices", but must get it when I explain it. Another "bad" thing about users not able to download apps from the appstore is that we have like a thousand "parking-apps" in our country and I have to buy all apps in Apple Business Manager, it's OK, but can be tiresome. For example we just traveled to another country where users wanted to take an Uber or a Bolt car, so they had to call be to buy and deploy the app, not very convenient. I made that mistake once, but now I bought tons of apps in business manager.. but just something to be aware of.
In terms of the Apple-ID itself, it's great and easy to use and manage for users, it's not that good in terms of icloud stogare since we can't buy more even if we want to. Continuity stuff is getting better every year, so overall great. Most of our users use personal Apple-IDs on their devices however. I mainly wanted to set up managed Apple-IDs to avoid having to help users manually create their Apple-ID/iCloud account where they lose the password etc.
