On the video it was slow, because the mobile was in a very unconvenient position for typing (it was placed on the table in front of the camera). Additionally, I haven't used it for several days, so I was little out of training
If you hold it in the other hand and got enough practise, you can easily type as fast as on the hardware keyboard.
My opinion, and some other people's that have tried it, is, that typing speed is ok after some warm-up.
If you put the entire keyboard onto the visible screen, it has both advantages and disadvantages (especially with 320 px. width, you would press 3 buttons at once). I have tried that approach too, but even if it may look usable on the emulator, on the G1 it is real torture that way.
-> my finger is 1,6 cm wide, the screen is 4,5 cm wide.
Sticky Note Cork&Orc [Android Market] : http://www.youtube.com/watch?v=ewWaquAwZQY