I thought the bun made her look older and stronger. You don't want a sexy captain. You want a tough old lady.
After she got that bob, she looked like a suburban housewife. They should have styled it more, given it some kind of body... like FutureJaneway's hair.
While we're on the subject: B'Elanna's hair wavy (like in Caretaker) was much better looking than when it was straightened out. And Chakotay is 1,000 times sexier with his hair brushed forward.