Findings so far...in order of severity (descending).

1. While some of the keys were fairly unresponsive at first but have gotten better over time, my S key is still very unresponsive; I have to press it properly hard for it to register. K and U are almost as bad. This is my number one worry right now as most of the other annoyances are likely fixable by tweaking the software.

2. Occasionally, a key gets stuck down. No matter what I do short of disconnecting the keyboard (which doesn't always work), I get an endless input of whichever key. So far I've had this happen on several character keys or space, but also backspace (!).
Note: I also sometimes see this with the terminal VKB. When that happens, pressing the stuck key again stops the repetition.

3. Now and then, keyboard stops working until reconnected.

4. Quick consecutive keypresses result in the first character being double-registered. Like, quickly press l then e, result is lle. My repeat delays in the settings are set to the highest possible values, yet this still happens.

5. When performing a Ctrl+a Ctrl+x -combo or similar, I have to lift Ctrl key between pressing a and x; otherwise the second keypress is treated as non-modifier input (select all and "x").

6. The bottom left corner of the keyboard has its own backlight, separate from the rest?
See suggestion at the end of this post

7. When the keyboard is fitted in the same orientation as on the N900 (device rotated 90 degrees to the left), the keyboard blocks flash even when in open position. I then tried rotating the keyboard to the other side, which left the flash led unobstructed, but the display didn't rotate so it was upside down. The landscape lock when keyboard is open is probably the culprit?

Has anyone else encountered these?

Suggestion: shift/Fn function like on the N900
As in, press shift or Fn once and it will apply that modifier to the next keypress (unless the next keypress is the same modifier again which cancels it).
EDIT:
It already seems to have this; pressing Ctrl lights up the left Fn key, pressing Ctrl again turns the light off. While the light is on, the next keypress has Ctrl modifier. Very nice.