How good is a thumb keyboard

Well, it's not the one you would like to have if you want to type 60 WPM. Here is what an actual owner of a Q1 Ultra says about it:

Mixed feelings on the keyboard. For short text like quick emails, it's fine. For something like entering a strong password, with mixed-case letters, numbers, and symbols, it's torture since there aren't dedicated number keys and almost all symbols require pressing another button first. It's especially bad for passwords that are hidden on the screen since you can't be quite sure if you didn't hit the wrong key or get a symbol to show up. So I'd say that it's very nice to have it there compared with not having a keyboard at all, but it's not something I'd want to use too often. Someone who is more used to typing on similar keyboards (like Blackberrys) might find it more natural than I do.

Just what I said a long time ago. There should be people out there making more than 20 WPM in a Blackberry but if you are into write long texts I doubt that 20 WPM is going to be enough for you. So do not be fool with "It has a keyboard" check first if you can function with that keyboard. That's all I'm saying.