Having played for an extended period of time with the Incredible (and as the owner of a Droid) I have to agree with the earlier assessment that it is far from a must-switch.
The Incredible certainly is a snappy performer with the faster processor, but having put both the Droid and Incredible side-by-side, I actually think the Droid's screen is slightly better. With the brightness set at the same level and in indoor light, the Droid's display seems to be a bit cleaner.
For example, on a website with a dark background and white boxes for text, the edges of the white boxes on the Droid are straight and clean, while the edges of the boxes on the Incredible show a slight pixel effect. That effect was also visible throughout the white box while the Droid's screen showed no such pixelation. I also found that while the colors on the Incredible seemed to be a bit more vibrant, there was also a tendency for whites to look a bit blue.
I know I might be in the minority, but I actually do like the Sense UI, which adds some very nice features (which have been described in several reviews).
However I don't think the increased performance (which could also be addressed if you're willing to root your Droid and overclock the processor) and Sense make for a compelling reason yet to ditch the Droid and jump to the Incredible.
Now, if you're willing to jump to Sprint, the Evo may be an upgrade worth considering, especially since they have a program in place that will actually pay you for turning in your phone. At CTIA I was told that if I walked into a Sprint store and turned in my Droid I would get over $100 toward the purchase of a new phone. It probably won't have quite that much value this summer, but it still might be a nice chunk of change.
And don't go to sleep on the Galaxy S, which actually may have the best looking screen out there. For a couple of hours (before the Evo was announced) the Galaxy S was the toast of CTIA.