I think it depends on your experience and level of development, I've found that over the years my front delts were overpowering from all the pressing movements so bent over laterals are essential in my routine.
Done properly they are a great addition to your workout however from what I've seen most do it incorrectly.
Larry Scott's method is spot on and almost completely isolate the delts, after doing his method my delts are fried
[ame="http://www.youtube.com/watch?v=FHsa7WXfADs"]Larry Scott Shoulder Workout - YouTube[/ame]