For me the biggest benefit of thumb keys isn't finger strength, it's the fact that the thumb is separated from the rest of the hand. It's really easy to hit a thumb key while hitting any other key on the "main" part of the keyboard. Whereas on a traditional keyboard, typing something like shift-T or ctrl-R requires stretching out your hand.
microtonal|5 months ago
Mirrored home row mods are even much nicer (IMO).