Same Same
Hey im running the same set up as you just with the 1.33ghz model. I suspect you should be okay with leopard considering the general architecture isn't that far from tiger which im assuming runs great as it does with me!
The only time the old Powerbook is going to struggle is when 10.6 hits the shelves (if its still ticking over by then that is). Especially if it drops PPC support as some rumours are suggesting, although if 10.6 is to be the last version in the os X series i dont see why Apple would do this.
Robxx