Working with the Dissolve Effect
Dissolve Effect in the Custom Animation does not look good in presentation. It simply doesn't look like a real dissolve. Since it does not work well alone, you can always experiment it out with other effects. One good example you can try is to have Dissolve and Spin effects together. The result is good if you have a circle-based logo. Here is a sample which you can take a look at. I named it "Spin the Dissolve". Take a look and you will understand why. ;)
http://pptheaven.mvps.org/blog/SpinTheDissolve.zip