I don't know if I ever use my left thumb to space. It kinda sits there, but unless i'm using a non-standard way of typing (ie, while i'm eating) then I can't image it ever doing anything. my right thumb always gets there first.

I use whatever shift I need to. Actually I don't. I always use left shift. I don't use right shift unless I'm doing html or making smilies 8) <>;D;D A B C D E F G H I J K L M N O P Q R S T U V W X Y Z.