I use freemind to manager my software development. I use the physical style to mark the knowledge node and the task node, but the subtask nodes and knowledge details nodes can't inherit the style from their parent. So I must set the style after inserting a new node again and again.
I've met the same problem, and working it around with keyboard currently.
I have heavily customized styles and keyboard mapping, so I can workaround this fast (with two keystrokes):
1. Shift+Right (or Shift+Left, if cursor is on left from root) selects whole tree
2. Ctrl+<number> gives whole selection new style.
Though this will be great if real styles were really supported (like css, not just formatting templates written inline like html nodes attributes) and inheritance can be set not just for node style but for each node property (in style editor to and should be added, meaning inherit from parent), this doesn't annoy me too much.