I have lots of problems with Microsoft but the Minecraft transition was handled very responsibly.

I ran into problems because some time before the transition happened some bot use my email address to sign up for an XBox account, in German for some reason. So I have to first do an account takeover on some bot account that has been used for no doubt unsavory purposes meaning my Minecraft account is now tied to something that's likely to be randomly locked. Also, some communication has to be done in German because there is no way to change the original language set on the account, although most pages can be converted to English if I look through the various settings pages. Email is always in German though.

Also, can I say what a mess the whole Microsoft account thing is? There's at least three different systems kinda duct taped together and settings are scattered seemingly at random among those systems. Want to connect your Java Minecraft instance to a server you are running? Be ready to dive through pages of kid protection and security settings looking for the option that lets you do that again. Also, logging in used to be "enter your username and password when the game starts", but now involves a bunch of bouncing around half a dozen or so Microsoft pages getting redirects that fail 60% of the time for no stated reason. It's kinda killed any enthusiasm I have for checking out new releases, just knowing that I'm going to waste 10 minutes just trying to get the damn login working again.

Mine wasn't. I lost my main account as I couldn't verify I owned it given it was bought on a whim years ago through a giftcard, and they didn't have many recovery methods for those users. Then they permanently deleted the account after the transfer window was over. Luckily I had a second account I could transfer, but even if I could transfer the other account, you cannot have multiple Minecraft accounts tied to a single Microsoft account and having multiple Microsoft accounts is against TOS.

The biggest issue I have with it was the lack of support for multiple accounts a la World of Warcraft style: why do I need 3 Microslop accounts?

I would agree.

They honored my account, and I originally bought the game when you had to send Notch money directly for him to send you a copy.

Microsoft was great in this instance.

barely made it myself. Turns out the MS username namespace didn't allow all minecraft names. I repeatedly failed migration because it was trying to auto-port an illegal username. the error was of course entirely opaque.

I don't love that I need a Microsoft account to log into minecraft, but the alternative was losing it permanently.

don’t know why you’re getting downvoted, they gave legacy users literal years to migrate