I don't use thumb typing, I'm usually using the keyboard as on a normal laptop. Also, I don't type much for my use cases, especially while traveling (my main usage for the Pocket). The keyboard is mostly fine, but takes some time to get used and I keep making typing mistakes every now and then, much more than on my 17" home laptop. But I used it on and off for just 3-4 weeks. In general, same issues with some weird/small keys as described earlier.

Battery life is quite good in my opinion, but that depends very much on usage, how it is measured, external temperature, tweaks, etc...
I did not make any real measurements, but on my last trip I watched 3 episodes of a tv serie (so cpu intensive task for 3 hours) and still had battery left; I think that for normal office usage it can last several hours. I don't believe though that it can reach the 12 hours duration that I sometimes read on the internet (not sure it if was initially advertised like that by GPD); perhaps if left untouched...