|I don't know - I didn't even know there was a problem with them. All I know is that they worked well for me when i was working with them over the last 2~3 weeks
For those sorts of small things, I find the NLA too messy. It's much nicer to just rotate the controller bone to the position I want (the amount that the hand is closed) and then just keyframe the controller bone. It gives instant feedback within the 3D view, and it's easy to manipulate the timing etc. within the action window, with the rest of the bones. Its also much harder in the NLA to blend just partially - i.e. if I just wanted the hand in between completely flat, and a closed fist.
Here's a quick .blend file I found in my pile of tests - may help clarify what I mean: http://reblended.com/www/broken/etc/actionconstraint_fingers.blend.zip