good question, IMHO good ukemi doesnt just mean taking good falls, it also means being able to give a good strong comitted attack and be centerd and sensitive enough to respond to what nage is doing without anticipation. so in that respect ukemi teaches you alot of thing that you can use when you are nage such as . timing , sensitivity , responsiveness and conection. pluss the better your ukemi is the harder you can train and still be safe. and there is alot you can learn from taking ukemi from higher ranking people.
if you would like to do some reading on ukemi there is a great article by Tres Hofmeister on the bujindesign web site look under news letter
have fun train hard