I have played with the droid and the droid eris. I wound up buying the eris for the following reasons:
* The droid is bulkier, heavier, and has squared edges compared to the eris, making it not fit well in a pocket.
* The keyboard on the droid is pretty much all suck. It's too flat to easily type on and it's offset by the big control pad on the right, forcing you to hold the thing awkwardly. essentially, the keyboard is so bad that I wound up using the touchscreen keyboard instead (which is actually very good)
* The sense UI in the eris makes for a generally more pleasurable experience.
* the camera took blurry pictures and took like 15 seconds to finish taking the picture before you could take another picture.
This isn't to say that the droid is a bad phone. I absolutely love the screen resolution and the processor is one of the fastest on the market. I just didn't like that it was so bulky and had a useless keyboard. If motorolla released a new droid that is smaller, had rounded edges, and just had the touchscreen and no keyboard, I'd probably be all over it. For now, I'm sticking with the eris though.