Like a lot of Whirlpool dishwashers with diverter motors, mine was leaking from the diverter valve. It was a slow leak, and I only discovered it because I was fixing another problem with the dishwasher (it wouldn't drain, because the drain hose was clogged with grease).
The repair was relatively straightforward. It took me about 2.5 hours from start to finish. It would have taken less time, but this was my first time fixing a dishwasher and I was also cleaning it as I went along (filters, spray arms, etc). The only hard part was getting the sump to seat properly in the tub -- it's a tight fit, I had to push really hard, even though I coated the seal with liquid detergent to help it along.
I'm also going to install a dishwasher pan from Leak Guard under the dishwasher, which will catch any future leaks and direct them out the front of the dishwasher where I can easily see them. I'm also planning to install a leak detector under the dishwasher, too, just in case.
Well anyway, it's fixed now, and it doesn't leak anymore!