I've got one of these, and I've generally been pretty pleased with it, typing wise.
I can type pretty quickly on the physical keyboard, and being a slider phone the screen itself is still a high proportion of the phone's surface area. However, I've also got a BB Playbook (so no physical keyboard), and I find typing on that to be fairly good too, especially with the word hinting.
Thus I find myself in a quandary about whether to go for a physical keyboard on my next phone. If I were buying a keyboard-less device the on screen one would have to be at least as good as the Playbook. If I were buying something with a physical keyboard it would have to be slider phone - I don't want to lose that much screen space. No one is doing slider phones these days, not even RIM :-(
So I guess if the on screen keyboard were as good as or better (add Swype?) than the Playbook's then I'd go with no physical keyboard. Which opens a lot of choice - Android, MS, Apple and BB10! Unless someone reproduces the keyboard arrangement that the Psion 5 had - best ever, never repeated (Psion owns the patent on it...).