I hate that feature :-(
It means I can't hold down the "d" key any more to delete mail
in an xterm. So bulk mail reading is slower now.

Occasionally I hold it by accident, due to habit on normal keyboards and the fact that cursor keys for scrolling through mail do repeat, and some weird unwanted thing happens when it sends "#" :-(

Auto-repeat has changed so it still works on some keys (arrows, enter), but then you get the habit of expect it to work with letters

Can't hold down Space either when using a text editor, to indent, and entering a run of "-" or "=" to underline some text in a plain text message is really fiddly now too :-(

The least they could have done was an option in Settings to turn "long keys" off.

That, and the can't-uncapitalize-first-letter-when-auto-capitalizing change is also really annoying. Practically every message I write, at least one word, I find myself entering a dummy letter to go back and delete after the word is written. :-(