i haven't been doing ut as long as most on this forum, but i have found that i get different results doing ut along with my regular eating habits, ut with limited food intake, and ut fasts with only urine and water. i think they all have their place and it depends on your goals and your circumstances which is the most appropriate at the time.
one thing i would mention is that when i only take urine and water (i haven't gone more than two days yet, but plan to when i have the opportunity), some profoundly powerful emotional stuff comes to the surface whether i want it to or not. just something to be prepared for. :)