I am using the Geek Hand keymappings (after unlearning the default mappings) and love it. Though my question likely is independent of using keymappings. I use my Twiddler with my left hand.
I have a hard time getting my thumb on the shift button (or any of the upper buttons) when using the R column. I'm thinking of remapping shift lock to one of the lesser used symbols, but curious if anyone else has had ergonomic questions on using the top buttons. Maybe I just need more hand exercise ...